U.S. patent application number 17/734960 was filed with the patent office on 2022-08-18 for semiconductor device and semiconductor memory device.
This patent application is currently assigned to Kioxia Corporation. The applicant listed for this patent is Kioxia Corporation. Invention is credited to Akifumi GAWASE, Tomoki ISHIMARU, Kazuhiro MATSUO, Shinji MORI, Keiichi SAWA.
Application Number | 20220262954 17/734960 |
Document ID | / |
Family ID | |
Filed Date | 2022-08-18 |
United States Patent
Application |
20220262954 |
Kind Code |
A1 |
ISHIMARU; Tomoki ; et
al. |
August 18, 2022 |
SEMICONDUCTOR DEVICE AND SEMICONDUCTOR MEMORY DEVICE
Abstract
A semiconductor device of an embodiment includes a first
electrode, a second electrode, a first metallic region provided
between the first electrode and the second electrode and includes
at least one metallic element selected from the group consisting of
indium (In), gallium (Ga), zinc (Zn), aluminum (Al), magnesium
(Mg), manganese (Mn), titanium (Ti), tungsten (W), molybdenum (Mo),
and tin (Sn), a second metallic region provided between the first
metallic region and the second electrode and includes the at least
one metallic element, a semiconductor region provided between the
first metallic region and the second metallic region and includes
the at least one metallic element and oxygen (O), an insulating
region provided between the first metallic region and the second
metallic region and is surrounded by the semiconductor region, a
gate electrode surrounding the semiconductor region, and a gate
insulating layer provided between the semiconductor region and the
gate electrode.
Inventors: |
ISHIMARU; Tomoki;
(Yokkaichi, JP) ; MORI; Shinji; (Nagoya, JP)
; MATSUO; Kazuhiro; (Kuwana, JP) ; SAWA;
Keiichi; (Yokkaichi, JP) ; GAWASE; Akifumi;
(Kuwana, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kioxia Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Kioxia Corporation
Tokyo
JP
|
Appl. No.: |
17/734960 |
Filed: |
May 2, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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17022328 |
Sep 16, 2020 |
11349033 |
|
|
17734960 |
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International
Class: |
H01L 29/786 20060101
H01L029/786; H01L 27/108 20060101 H01L027/108; H01L 29/267 20060101
H01L029/267; H01L 29/08 20060101 H01L029/08; H01L 29/417 20060101
H01L029/417; H01L 29/40 20060101 H01L029/40 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 2020 |
JP |
2020-052249 |
Claims
1. A semiconductor device comprising: a first electrode; a second
electrode; a first oxide semiconductor region provided between the
first electrode and the second electrode, the first oxide
semiconductor region including at least one predetermined element
selected from the group consisting of indium (In), silicon (Si),
and tin (Sn); a second oxide semiconductor region provided between
the first oxide semiconductor region and the second electrode, the
second oxide semiconductor region including the at least one
predetermined element; a third oxide semiconductor region provided
between the first oxide semiconductor region and the second oxide
semiconductor region, the third oxide semiconductor region
including or not including the at least one predetermined element,
the third oxide semiconductor region having a concentration of the
at least one predetermined element lower than a concentration of
the at least one predetermined element in the first oxide
semiconductor region and the second oxide semiconductor region, the
third oxide semiconductor region including a first portion and a
second portion surrounded by the first portion, and a first
distance between the first oxide semiconductor region and the
second oxide semiconductor region between which the first portion
is sandwiched is different from a second distance between the first
oxide semiconductor region and the second oxide semiconductor
region between which the second portion is sandwiched; a gate
electrode surrounding the third oxide semiconductor region; and a
gate insulating layer provided between the third oxide
semiconductor region and the gate electrode.
2. The semiconductor device according to claim 1, wherein the first
distance is smaller than the second distance.
3. The semiconductor device according to claim 1, wherein the
concentration of the at least one predetermined element in the
first oxide semiconductor region and the second oxide semiconductor
region is equal to or higher than 1.times.10.sup.17 cm.sup.-3 and
is equal to or lower than 1.times.10.sup.21 cm.sup.-3.
4. The semiconductor device according to claim 1, wherein the third
oxide semiconductor region and the first electrode are spaced apart
from each other, and the third oxide semiconductor region and the
second electrode are spaced apart from each other.
5. The semiconductor device according to claim 1, wherein the first
oxide semiconductor region, the second oxide semiconductor region,
and the third semiconductor region include indium (In), gallium
(Ga), and zinc (Zn).
6. A semiconductor device comprising: a first electrode; a second
electrode; a first oxide semiconductor region provided between the
first electrode and the second electrode; a second oxide
semiconductor region provided between the first oxide semiconductor
region and the second electrode; a third oxide semiconductor region
provided between the first oxide semiconductor region and the
second oxide semiconductor region, the third oxide semiconductor
region having electrical resistance higher than electrical
resistances of the first oxide semiconductor region and the second
oxide semiconductor region, and the third oxide semiconductor
region including a first portion and a second portion surrounded by
the first portion; a gate electrode surrounding the third oxide
semiconductor region; and a gate insulating layer provided between
the third oxide semiconductor region and the gate electrode,
wherein a first distance between the first electrode and the first
portion between which the first oxide semiconductor region is
sandwiched is larger than a second distance between the first
electrode and the second portion between which the first oxide
semiconductor region is sandwiched.
7. The semiconductor device according to claim 6, wherein a third
distance between the second electrode and the first portion between
which the second oxide semiconductor region is sandwiched is larger
than a fourth distance between the second electrode and the second
portion between which the second oxide semiconductor region is
sandwiched.
8. The semiconductor device according to claim 6, wherein the third
oxide semiconductor region and the first electrode are spaced apart
from each other, and the third oxide semiconductor region and the
second electrode are spaced apart from each other.
9. The semiconductor device according to claim 6, wherein the first
oxide semiconductor region and the second oxide semiconductor
region include at least one predetermined element selected from the
group consisting of indium (In), silicon (Si), and tin (Sn).
10. The semiconductor device according to claim 6, wherein the
first oxide semiconductor region, the second oxide semiconductor
region, and the third semiconductor region include indium (In),
gallium (Ga), and zinc (Zn).
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. Ser. No.
17/022,328, filed Sep. 16, 2020, which is based upon and claims the
benefit of priority from Japanese Patent Application No.
2020-052249, filed on Mar. 24, 2020, the entire contents of each of
which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a
semiconductor device and a semiconductor memory device.
BACKGROUND
[0003] An oxide semiconductor transistor in which a channel is
formed in an oxide semiconductor layer has an excellent property of
having an extremely small channel leakage current, in other words,
an extremely small off-leakage current, during off-operation. To
apply such an oxide semiconductor transistor to a transistor of a
memory device, further reduction of off-leakage current and
reduction of on-resistance are desired.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a schematic sectional view of a semiconductor
device of a first embodiment;
[0005] FIG. 2 is a schematic sectional view of the semiconductor
device of the first embodiment;
[0006] FIG. 3 is a schematic sectional view illustrating a
semiconductor-device manufacturing method of the first
embodiment;
[0007] FIG. 4 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0008] FIG. 5 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0009] FIG. 6 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0010] FIG. 7 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0011] FIG. 8 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0012] FIG. 9 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0013] FIG. 10 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0014] FIG. 11 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0015] FIG. 12 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0016] FIG. 13 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0017] FIG. 14 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0018] FIG. 15 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0019] FIG. 16 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the first
embodiment;
[0020] FIG. 17 is a schematic sectional view of a semiconductor
device of a comparative example;
[0021] FIG. 18 is a schematic sectional view of a semiconductor
device of a first modification of the first embodiment;
[0022] FIG. 19 is a schematic sectional view of a semiconductor
device of a second modification of the first embodiment;
[0023] FIG. 20 is a schematic sectional view of a semiconductor
device of a second embodiment;
[0024] FIG. 21 is a schematic sectional view of the semiconductor
device of the second embodiment;
[0025] FIG. 22 is a schematic sectional view of the semiconductor
device of the second embodiment;
[0026] FIG. 23 is a schematic sectional view illustrating a
semiconductor-device manufacturing method of the second
embodiment;
[0027] FIG. 24 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0028] FIG. 25 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0029] FIG. 26 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0030] FIG. 27 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0031] FIG. 28 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0032] FIG. 29 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0033] FIG. 30 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0034] FIG. 31 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0035] FIG. 32 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0036] FIG. 33 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0037] FIG. 34 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the second
embodiment;
[0038] FIG. 35 is a schematic sectional view of a semiconductor
device of a first modification of the second embodiment;
[0039] FIG. 36 is a schematic sectional view of a semiconductor
device of a second modification of the second embodiment;
[0040] FIG. 37 is a schematic sectional view of a semiconductor
device of a third embodiment;
[0041] FIG. 38 is a schematic sectional view of the semiconductor
device of the third embodiment;
[0042] FIG. 39 is a schematic sectional view of the semiconductor
device of the third embodiment;
[0043] FIG. 40 is a schematic sectional view illustrating a
semiconductor-device manufacturing method of the third
embodiment;
[0044] FIG. 41 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0045] FIG. 42 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0046] FIG. 43 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0047] FIG. 44 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0048] FIG. 45 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0049] FIG. 46 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0050] FIG. 47 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0051] FIG. 48 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0052] FIG. 49 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0053] FIG. 50 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0054] FIG. 51 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0055] FIG. 52 is a schematic sectional view illustrating the
semiconductor-device manufacturing method of the third
embodiment;
[0056] FIG. 53 is a schematic sectional view of a semiconductor
device of a first modification of the third embodiment;
[0057] FIG. 54 is a schematic sectional view of a semiconductor
device of a second modification of the third embodiment;
[0058] FIG. 55 is a schematic sectional view of a semiconductor
device of a third modification of the third embodiment;
[0059] FIG. 56 is a block diagram of a semiconductor memory device
of a fourth embodiment;
[0060] FIG. 57 is a schematic sectional view of a memory cell array
of the semiconductor memory device of the fourth embodiment;
[0061] FIG. 58 is a schematic sectional view of the memory cell
array of the semiconductor memory device of the fourth
embodiment;
[0062] FIG. 59 is a schematic sectional view of a first memory cell
of the semiconductor memory device of the fourth embodiment;
[0063] FIG. 60 is a schematic sectional view of a second memory
cell of the semiconductor memory device of the fourth
embodiment;
[0064] FIG. 61 is a schematic sectional view of a memory cell array
of a semiconductor memory device of a fifth embodiment;
[0065] FIG. 62 is a schematic sectional view of the memory cell
array of the semiconductor memory device of the fifth
embodiment;
[0066] FIG. 63 is a schematic sectional view of a first memory cell
of the semiconductor memory device of the fifth embodiment;
[0067] FIG. 64 is a schematic sectional view of a second memory
cell of the semiconductor memory device of the fifth
embodiment;
[0068] FIG. 65 is a schematic sectional view of a memory cell array
of a semiconductor memory device of a sixth embodiment;
[0069] FIG. 66 is a schematic sectional view of the memory cell
array of the semiconductor memory device of the sixth
embodiment;
[0070] FIG. 67 is a schematic sectional view of a first memory cell
of the semiconductor memory device of the sixth embodiment;
[0071] and
[0072] FIG. 68 is a schematic sectional view of a second memory
cell of the semiconductor memory device of the sixth
embodiment.
DETAILED DESCRIPTION
[0073] A semiconductor device of an embodiment includes a first
electrode, a second electrode, a first metallic region provided
between the first electrode and the second electrode, the first
metallic region including at least one metallic element selected
from the group consisting of indium (In), gallium (Ga), zinc (Zn),
aluminum (Al), magnesium (Mg), manganese (Mn), titanium (Ti),
tungsten (W), molybdenum (Mo), and tin (Sn), a second metallic
region provided between the first metallic region and the second
electrode, the second metallic region including the at least one
metallic element, a semiconductor region provided between the first
metallic region and the second metallic region, the semiconductor
region including the at least one metallic element and oxygen (O),
an insulating region provided between the first metallic region and
the second metallic region, the insulating region being surrounded
by the semiconductor region, a gate electrode surrounding the
semiconductor region, and a gate insulating layer provided between
the semiconductor region and the gate electrode.
[0074] Hereinafter, embodiments of the present disclosure will be
described with reference to the drawings. Note that the same or
similar components or the like are denoted by the same reference
signs, and explanation of components or the like that have been
explained once is omitted if appropriate, in the following
description.
[0075] Further, the present specification uses the term "upper" (or
above)" or "lower (or below)" in some portions for convenience's
sake. The term "upper (or above)" or "lower (or below)" indicates a
positional relationship relative to components in the drawings
merely, and does not define a positional relationship according to
gravity.
[0076] Qualitative analysis or quantitative analysis of a chemical
composition of each component forming a semiconductor device and a
semiconductor memory device in the present specification can be
achieved by secondary ion mass spectrometry (SIMS), energy
dispersive X-ray spectroscopy (EDX), or Rutherford back-scattering
spectroscopy (RBS), for example. Further, the thickness of each
component forming the semiconductor device and the semiconductor
memory device, a distance between the components, and the like can
be measured with a transmission electron microscope (TEM), for
example. Moreover, the electrical resistance of each component
forming the semiconductor device and the semiconductor memory
device can be measured by scanning spreading resistance microscopy
(SSRM), for example.
First Embodiment
[0077] A semiconductor device of a first embodiment includes a
first electrode, a second electrode, a first metallic region
provided between the first electrode and the second electrode, the
first metallic region including at least one metallic element
selected from the group consisting of indium (In), gallium (Ga),
zinc (Zn), aluminum (Al), magnesium (Mg), manganese (Mn), titanium
(Ti), tungsten (W), molybdenum (Mo), and tin (Sn), a second
metallic region provided between the first metallic region and the
second electrode, the second metallic region including the at least
one metallic element, a semiconductor region provided between the
first metallic region and the second metallic region, the
semiconductor region including the at least one metallic element
and oxygen (O), an insulating region provided between the first
metallic region and the second metallic region, the insulating
region being surrounded by the semiconductor region, a gate
electrode surrounding the semiconductor region, and a gate
insulating layer provided between the semiconductor region and the
gate electrode.
[0078] FIGS. 1 and 2 are schematic sectional views of the
semiconductor device of the first embodiment. FIG. 2 is a sectional
view taken along A-A' in FIG. 1. In FIG. 2, a horizontal direction
is referred to as a first direction, a depth direction is referred
to as a second direction, and a vertical direction is referred to
as a third direction.
[0079] The semiconductor device of the first embodiment is a
transistor 100. The transistor 100 is an oxide semiconductor
transistor in which a channel is formed in an oxide semiconductor.
In the transistor 100, a gate electrode is provided so as to
surround an oxide semiconductor in which a channel is formed. The
transistor 100 is a so-called surrounding gate transistor (SGT).
The transistor 100 is a so-called vertical transistor.
[0080] The transistor 100 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, a core
insulating region 24, a first interlayer insulating layer 26, a
second interlayer insulating layer 28, a first protective
insulating layer 30, and a second protective insulating layer
32.
[0081] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first
metallic region. The drain region 16 is one example of the second
metallic region. The channel region 18 is one example of the
semiconductor region. The core insulating region 24 is one example
of the insulating region.
[0082] The source electrode 10 is a metal or a metallic compound,
for example. The source electrode 10 is tungsten (W), for
example.
[0083] The drain electrode 12 is a metal or a metallic compound,
for example. The drain electrode 12 is tungsten (W), for
example.
[0084] The source region 14 is provided between the source
electrode 10 and the drain electrode 12. The source region 14 and
the source electrode 10 are in contact with each other. The source
region 14 and the source electrode 10 are electrically
connected.
[0085] The source region 14 is a metal. The source region 14 is a
metal of which oxide acts as a semiconductor. The source region 14
includes at least one metallic element selected from the group
consisting of indium (In), gallium (Ga), zinc (Zn), aluminum (Al),
magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn).
[0086] The drain region 16 is provided between the source region 14
and the drain electrode 12. The drain region 16 is in contact with
the drain electrode 12. The drain region 16 is electrically
connected to the drain electrode 12.
[0087] The drain region 16 is a metal. The drain region 16 is a
metal of which oxide acts as a semiconductor. The drain region 16
includes at least one metallic element selected from the group
consisting of indium (In), gallium (Ga), zinc (Zn), aluminum (Al),
magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn).
[0088] The drain region 16 is formed of the same metal as that
forming the source region 14. The drain region 16 includes the same
metallic element as that included in the source region 14.
[0089] The channel region 18 is provided between the source region
14 and the drain region 16. The channel region 18 is in contact
with the source region 14 and the drain region 16.
[0090] In the channel region 18, a channel serving as a current
path during on-operation of the transistor 100 is formed. The
channel region 18 extends along a direction toward the drain
electrode 12 from the source electrode 10, that is, along the third
direction. During on-operation of the transistor 100, a current
flows along the third direction in the channel region 18.
[0091] The channel region 18 is tube-shaped, for example.
[0092] A length of the channel region 18 along a direction toward
the drain electrode 12 from the source electrode 10, in other
words, a length of the channel region 18 along the third direction,
is equal to a distance (d1 in FIG. 1) between the source region 14
and the drain region 16 along the third direction. The distance d1
is equal to or larger than 20 nm and is equal to or smaller than
100 nm, for example.
[0093] The channel region 18 is an oxide semiconductor. The channel
region 18 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O).
[0094] The channel region 18 is an oxide of a metal forming the
source region 14 and the drain region 16. The channel region 18
includes the same metallic element as that included in the source
region 14 and the drain region 16. The channel region 18 is
amorphous, for example.
[0095] The source region 14 and the drain region 16 include indium
(In), gallium (Ga), and zinc (Zn), for example. The channel region
18 includes indium (In), gallium (Ga), zinc (Zn), and oxygen (O),
for example.
[0096] The atomic ratio of a sum of indium, gallium, and zinc in
metallic elements included in the source region 14 and the drain
region 16 is, for example, 90% or higher. For example, the source
region 14 and the drain region 16 do not include any element that
has a higher atomic ratio than any of indium, gallium, and
zinc.
[0097] The atomic ratio of a sum of indium, gallium, and zinc in
metallic elements included in the channel region 18 is, for
example, 90% or higher. The atomic ratio of a sum of indium,
gallium, and zinc in elements included in the channel region 18
except oxygen, is, for example, 90% or higher. For example, the
channel region 18 does not include any element that has a higher
atomic ratio than any of indium, gallium, and zinc, except
oxygen.
[0098] The gate electrode 20 is provided so as to surround the
channel region 18. The gate electrode 20 is provided around the
channel region 18.
[0099] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example. A length (d2 in FIG. 1) of the gate electrode 20 along
the third direction is equal to or larger than 20 nm and is equal
to or smaller than 100 nm, for example. The length d2 of the gate
electrode 20 along the third direction is the gate length of the
transistor 100.
[0100] The distance d1 between the source region 14 and the drain
region 16 along the third direction is equal to the length d2 of
the gate electrode 20 along the third direction, for example.
[0101] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example.
[0102] The gate insulating layer 22 is provided between the channel
region 18 and the gate electrode 20. The gate insulating layer 22
is provided so as to surround the channel region 18.
[0103] The gate insulating layer 22 is an oxide or an oxynitride,
for example. The gate insulating layer 22 is silicon oxide or
aluminum oxide, for example. The gate insulating layer 22 has a
thickness equal to or larger than 2 nm and is equal to or smaller
than 10 nm, for example.
[0104] The core insulating region 24 is provided between the source
region 14 and the drain region 16. The core insulating region 24 is
surrounded by the channel region 18. The core insulating region 24
is cylindrical, for example. The core insulating region 24 and the
source electrode 10 are spaced apart from each other. The core
insulating region 24 and the drain electrode 12 are spaced apart
from each other.
[0105] The core insulating region 24 is an oxide, a nitride, or an
oxynitride, for example. The core insulating region 24 is silicon
oxide, silicon nitride, or silicon oxynitride, for example.
[0106] The first interlayer insulating layer 26 is provided between
the source electrode 10 and the gate electrode 20. The first
interlayer insulating layer 26 is provided around the source region
14.
[0107] The first interlayer insulating layer 26 is an oxide, a
nitride, or an oxynitride, for example. The first interlayer
insulating layer 26 is silicon oxide, for example.
[0108] The second interlayer insulating layer 28 is provided
between the drain electrode 12 and the gate electrode 20. The
second interlayer insulating layer 28 is provided around the drain
region 16.
[0109] The second interlayer insulating layer 28 is an oxide, a
nitride, or an oxynitride, for example. The second interlayer
insulating layer 28 is silicon oxide, for example.
[0110] The first protective insulating layer 30 is provided between
the first interlayer insulating layer 26 and the gate electrode 20.
The first protective insulating layer 30 is provided around the
source region 14.
[0111] The first protective insulating layer 30 is an oxide, a
nitride, or an oxynitride, for example. The first protective
insulating layer 30 is formed of a material different from that
forming the first interlayer insulating layer 26, for example. The
first protective insulating layer 30 is silicon nitride, for
example.
[0112] The second protective insulating layer 32 is provided
between the second interlayer insulating layer 28 and the gate
electrode 20. The second protective insulating layer 32 is provided
around the drain region 16.
[0113] The second protective insulating layer 32 is an oxide, a
nitride, or an oxynitride, for example. The second protective
insulating layer 32 is formed of a material different from that
forming the second interlayer insulating layer 28, for example. The
second protective insulating layer 32 is silicon nitride, for
example.
[0114] Next, an example of a semiconductor-device manufacturing
method of the first embodiment will be described.
[0115] FIGS. 3 to 16 are schematic sectional views illustrating the
semiconductor-device manufacturing method of the first embodiment.
FIGS. 3 to 16 illustrate sections corresponding to the section
illustrated in FIG. 1.
[0116] First, a first tungsten film 40, a first silicon oxide film
42, a first silicon nitride film 44, a polycrystalline silicon film
46, a second silicon nitride film 48, and a second silicon oxide
film 50 are formed sequentially in the stated order (FIG. 3). The
first tungsten film 40, the first silicon oxide film 42, the first
silicon nitride film 44, the polycrystalline silicon film 46, the
second silicon nitride film 48, and the second silicon oxide film
50 are formed by a chemical vapor deposition process (CVD process),
for example.
[0117] Subsequently, boring is performed from the surface of the
second silicon oxide film 50 to form a first opening 52 extending
to the first tungsten film 40 (FIG. 4). The first opening 52 is
formed using a lithography process and a reactive ion etching
process (RIE process), for example.
[0118] Subsequently, a first metallic film 54 is buried in the
first opening 52 (FIG. 5). The first metallic film 54 is a metal of
which oxide acts as an oxide semiconductor. The first metallic film
54 includes indium (In), gallium (Ga), and zinc (Zn), for
example.
[0119] Subsequently, a portion of the first metallic film 54 on the
surface of the second silicon oxide film 50 is removed (FIG. 6).
The portion of the first metallic film 54 is removed by a chemical
mechanical polishing process (CMP process), for example.
[0120] Subsequently, a second opening 56 is formed in the first
metallic film 54 (FIG. 7). The second opening 56 is formed using a
lithography process and a RIE process, for example.
[0121] Subsequently, a third silicon oxide film 58 is buried in the
second opening 56 (FIG. 8). The third silicon oxide film 58 is
formed by a CVD process, for example.
[0122] Subsequently, the parts of the third silicon oxide film 58
on the surface of the second silicon oxide film 50 and in a portion
of the second opening 56 are removed (FIG. 9). The parts of the
third silicon oxide film 58 are removed by a RIE process, for
example.
[0123] Subsequently, a second metallic film 60 is buried in the
second opening 56 (FIG. 10). The second metallic film 60 has the
same chemical composition as that of the first metallic film 54.
Hereinafter, the second metallic film 60 will be described as being
included in the first metallic film 54. The second metallic film 60
is formed through deposition by a CVD process and polishing by a
CMP process, for example.
[0124] Subsequently, a second tungsten film 62 is formed on the
second silicon oxide film 50 and the first metallic film 54 (FIG.
11). The second tungsten film 62 is formed by a CVD process, for
example.
[0125] Subsequently, the polycrystalline silicon film 46 is removed
(FIG. 12). The polycrystalline silicon film 46 is removed by a wet
etching process, for example.
[0126] Subsequently, a portion of the first metallic film 54, which
is exposed to a region where the polycrystalline silicon film 46
has been removed, is oxidized (FIG. 13). The oxidization of the
first metallic film 54 forms an oxide semiconductor region 64. The
oxide semiconductor region 64 serves as the channel region 18.
[0127] Subsequently, a part of the first silicon nitride film 44
and a part of the second silicon nitride film 48 are removed to
make the first silicon nitride film 44 and the second silicon
nitride film 48 thinner (FIG. 14). The respective parts of the
first silicon nitride film 44 and the second silicon nitride film
48 are removed by a wet etching process, for example.
[0128] Subsequently, a fourth silicon oxide film 66 is formed so as
to be in contact with the oxide semiconductor region 64 (FIG. 15).
The fourth silicon oxide film 66 is formed by a CVD process, for
example. The fourth silicon oxide film 66 serves as the gate
insulating layer 22.
[0129] Subsequently, a third tungsten film 68 is formed so as to be
in contact with the fourth silicon oxide film 66 (FIG. 16). The
third tungsten film 68 is formed by a CVD process, for example. The
third tungsten film 68 serves as the gate electrode 20.
[0130] By the above-described manufacturing method, the transistor
100 illustrated in FIG. 1 is formed.
[0131] Next, functions and effects of the semiconductor device of
the first embodiment will be described.
[0132] FIG. 17 is a schematic sectional view of a semiconductor
device of a comparative example. The semiconductor device of the
comparative example is a transistor 900. The transistor 900 is an
oxide semiconductor transistor in which a channel is formed in an
oxide semiconductor. The transistor 900 is a so-called SGT
including a gate electrode provided so as to surround an oxide
semiconductor in which a channel is formed. The transistor 900 is a
so-called vertical transistor.
[0133] The transistor 900 is different from the transistor 100 of
the first embodiment in that the core insulating region 24 is not
included. The transistor 900 is different from the transistor 100
also in that each of the source region 14 and the drain region 16
is not a metal, but an oxide semiconductor.
[0134] The transistor 900 does not include the core insulating
region 24. Thus, the channel region 18 has a large thickness.
Because of the large thickness of the channel region 18, a leakage
current is more likely to flow through a region remote from the
gate electrode 20 in the channel region 18 during off-operation of
the transistor 900. Therefore, it is difficult to reduce an
off-leakage current.
[0135] Further, in the transistor 900, each of the source region 14
and the drain region 16 is an oxide semiconductor. Thus, a junction
between the source electrode 10 and the source region 14 is a
metal-semiconductor junction, which makes it difficult to reduce
contact resistance. Likewise, a junction between the drain
electrode 12 and the drain region 16 is a metal-semiconductor
junction, which makes it difficult to reduce contact resistance.
Therefore, it is difficult to reduce on-resistance.
[0136] In the transistor 100 of the first embodiment, the core
insulating region 24 is provided inside the channel region 18. This
can reduce the thickness of the channel region 18. Therefore, it is
easy to reduce an off-leakage current.
[0137] Further, each of the source region 14 and the drain region
16 of the transistor 100 of the first embodiment is a metal. Thus,
a junction between the source electrode 10 and the source region 14
is a metal-metal junction. For this reason, it is easy to reduce
contact resistance. Likewise, a junction between the drain
electrode 12 and the drain region 16 is a metal-metal junction, and
for this reason, it is easy to reduce contact resistance.
Therefore, it is easy to reduce on-resistance.
[0138] Moreover, the channel region 18 is formed of an oxide of a
metal forming the source region 14 and the drain region 16. Thus,
the channel region 18 can be formed by oxidization of a metal
forming the source region 14 and the drain region 16. This makes an
interface between the channel region 18 and the source region 14
and an interface between the channel region 18 and the drain region
16 stable with fewer defects. Therefore, resistance at each
interface is reduced and on-resistance is reduced.
[0139] The transistor 100 of the first embodiment can reduce an
off-leakage current and can reduce on-resistance as compared to the
transistor 900 of the comparative example.
[0140] FIG. 18 is a schematic sectional view of a semiconductor
device of a first modification of the first embodiment. The
semiconductor device of the first modification is a transistor
101.
[0141] The transistor 101 is different from the transistor 100 of
the first embodiment in that a part of the source region 14 and the
gate electrode 20 positionally overlap each other along the third
direction and that a part of the drain region 16 and the gate
electrode 20 positionally overlap each other along the third
direction. Thus, a distance (d1 in FIG. 18) between the source
region 14 and the drain region 16 along the third direction is
smaller than a length (d2 in FIG. 18) of the gate electrode 20
along the third direction. The distance d1 between the source
region 14 and the drain region 16 along the third direction is
equal to or smaller than 0.9 times the length d2 of the gate
electrode 20 along the third direction, for example.
[0142] In the transistor 101 of the first modification, the source
region 14 and the gate electrode 20 overlap each other and the
drain region 16 and the gate electrode 20 overlap each other. As a
result of this, offsets between the source region 14 and the gate
electrode 20 and between the drain region 16 and the gate electrode
20 due to variation in process, for example, are unlikely to occur.
Therefore, a transistor with stable on-resistance can be
achieved.
[0143] FIG. 19 is a schematic sectional view of a semiconductor
device of a second modification of the first embodiment. The
semiconductor device of the second modification is a transistor
102.
[0144] The transistor 102 is different from the transistor 100 of
the first embodiment in that the source region 14 and the gate
electrode 20 do not positionally overlap each other along the third
direction and in that the drain region 16 and the gate electrode 20
do not positionally overlap each other along the third direction.
Thus, a distance (d1 in FIG. 19) between the source region 14 and
the drain region 16 along the third direction is larger than a
length (d2 in FIG. 19) of the gate electrode 20 along the third
direction. The distance d1 between the source region 14 and the
drain region 16 along the third direction is equal to or larger
than 1.1 times the length d2 of the gate electrode 20 along the
third direction, for example.
[0145] The configuration of the transistor 102 of the second
modification can reduce the volume of the gate electrode 20. Thus,
particularly in a case where a material of the gate electrode 20 is
a metal, the stress of the transistor 102 is relieved. Therefore, a
highly-reliable transistor can be achieved.
[0146] As described above, according to the first embodiment and
its modifications, a transistor that can reduce an off-leakage
current and can reduce on-resistance can be achieved.
Second Embodiment
[0147] A semiconductor device of a second embodiment includes a
first electrode, a second electrode, a first oxide semiconductor
region provided between the first electrode and the second
electrode, a second oxide semiconductor region provided between the
first oxide semiconductor region and the second electrode, a third
oxide semiconductor region provided between the first oxide
semiconductor region and the second oxide semiconductor region, the
third oxide semiconductor region having electrical resistance
higher than those of the first oxide semiconductor region and the
second oxide semiconductor region, and the third oxide
semiconductor region including a first portion and a second portion
surrounded by the first portion in which a first distance between
the first oxide semiconductor region and the second oxide
semiconductor region between which the first portion is sandwiched
is smaller than a second distance between the first oxide
semiconductor region and the second oxide semiconductor region
between which the second portion is sandwiched, a gate electrode
surrounding the third oxide semiconductor region, and a gate
insulating layer provided between the third oxide semiconductor
region and the gate electrode.
[0148] FIGS. 20 to 22 are schematic sectional views of the
semiconductor device of the second embodiment. FIG. 21 is a
sectional view taken along B-B' in FIG. 20. FIG. 22 is a sectional
view taken along C-C' in FIG. 20. In FIG. 20, a horizontal
direction is referred to as a first direction, a depth direction is
referred to as a second direction, and a vertical direction is
referred to as a third direction.
[0149] The semiconductor device of the second embodiment is a
transistor 200. The transistor 200 is an oxide semiconductor
transistor in which a channel is formed in an oxide semiconductor.
In the transistor 200, a gate electrode is provided so as to
surround an oxide semiconductor in which a channel is formed. The
transistor 200 is a so-called SGT. The transistor 200 is a
so-called vertical transistor.
[0150] The transistor 200 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, a first
interlayer insulating layer 26, and a second interlayer insulating
layer 28. The channel region 18 includes a surface portion 18a and
a core portion 18b.
[0151] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first oxide
semiconductor region. The drain region 16 is one example of the
second oxide semiconductor region. The channel region 18 is one
example of the third oxide semiconductor region. The surface
portion 18a is one example of the first portion. The core portion
18b is one example of the second portion.
[0152] The source electrode 10 is a metal or a metallic compound,
for example. The source electrode 10 is tungsten (W), for
example.
[0153] The drain electrode 12 is a metal or a metallic compound,
for example. The drain electrode 12 is tungsten (W), for
example.
[0154] The source region 14 is provided between the source
electrode 10 and the drain electrode 12. The source region 14 and
the source electrode 10 are in contact with each other. The source
region 14 and the source electrode 10 are electrically
connected.
[0155] The source region 14 is an oxide semiconductor. The source
region 14 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O). The source region 14
is amorphous, for example.
[0156] The drain region 16 is provided between the source region 14
and the drain electrode 12. The drain region 16 is in contact with
the drain electrode 12. The drain region 16 is electrically
connected to the drain electrode 12.
[0157] The drain region 16 is an oxide semiconductor. The drain
region 16 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O).
[0158] The drain region 16 is formed of the same oxide
semiconductor as that forming the source region 14. The drain
region 16 includes the same metallic element as that included in
the source region 14. The drain region 16 is amorphous, for
example.
[0159] The channel region 18 is provided between the source region
14 and the drain region 16. The channel region 18 is in contact
with the source region 14 and the drain region 16.
[0160] The channel region 18 is spaced apart from the source
electrode 10. The channel region 18 is spaced apart from the drain
electrode 12.
[0161] In the channel region 18, a channel serving as a current
path during on-operation of the transistor 200 is formed. The
channel region 18 extends along a direction toward the drain
electrode 12 from the source electrode 10, that is, along the third
direction. During on-operation of the transistor 200, a current
flows along the third direction in the channel region 18.
[0162] The channel region 18 includes the surface portion 18a and
the core portion 18b. The core portion 18b is surrounded by the
surface portion 18a. A part of the core portion 18b on a side close
to the source region 14 is surrounded by the source region 14. A
part of the core portion 18b on a side close to the drain region 16
is surrounded by the drain region 16.
[0163] A first distance (d3 in FIG. 20) along the third direction
between respective portions of the source region 14 and the drain
region 16 between which the surface portion 18a is sandwiched is
smaller than a second distance (d4 in FIG. 20) along the third
direction between respective portions of the source region 14 and
the drain region 16 between which the core portion 18b is
sandwiched. In other words, a length of the surface portion 18a
along the third direction is smaller than a length of the core
portion 18b along the third direction.
[0164] The first distance d3 is equal to or larger than 20 nm and
is equal to or smaller than 100 nm, for example. The second
distance d4 is equal to or larger than 1.2 times the first distance
d3 and is equal to or smaller than 2.0 times the first distance d3,
for example.
[0165] The channel region 18 is an oxide semiconductor. The channel
region 18 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O).
[0166] The channel region 18 is formed of the same oxide
semiconductor as that forming the source region 14 and the drain
region 16. The channel region 18 includes the same metallic element
as that included in the source region 14 and the drain region 16.
The channel region 18 is amorphous, for example.
[0167] The channel region 18 has electrical resistance higher than
the electrical resistance of the source region 14. The channel
region 18 has electrical resistance higher than the electrical
resistance of the drain region 16.
[0168] In other words, the source region 14 has electrical
resistance lower than the electrical resistance of the channel
region 18. The drain region 16 has electrical resistance lower than
the electrical resistance of the channel region 18.
[0169] The channel region 18 has a carrier concentration lower than
the carrier concentration of the source region 14. The channel
region 18 has a carrier concentration lower than the carrier
concentration of the drain region 16.
[0170] In other words, the source region 14 has a carrier
concentration higher than the carrier concentration of the channel
region 18. The drain region 16 has a carrier concentration higher
than the carrier concentration of the channel region 18.
[0171] For example, the source region 14 and the drain region 16
include at least one predetermined element selected from the group
consisting of indium (In), silicon (Si), and tin (Sn). The channel
region 18 either includes the above-stated predetermined element,
or does not include the above-stated predetermined element. The
concentration of the above-stated predetermined element in the
source region 14 and the drain region 16 is higher than the
concentration of the above-stated predetermined element in the
channel region 18.
[0172] The above-stated predetermined element functions as a donor
that emits electrons in an oxide semiconductor. The concentration
of the above-stated predetermined element in the source region 14
and the drain region 16 is equal to or higher than
1.times.10.sup.17 cm.sup.-3 and is equal to or lower than
1.times.10.sup.21 cm.sup.-3, for example.
[0173] For example, the source region 14 and the drain region 16
include an oxide vacancy. The channel region 18 either includes an
oxide vacancy or does not include an oxide vacancy. The
concentration of oxide vacancy in the source region 14 and the
drain region 16 is higher than the concentration of oxide vacancy
in the channel region 18.
[0174] The oxide vacancy functions as a donor that emits electrons
in an oxide semiconductor.
[0175] The source region 14, the drain region 16, and the channel
region 18 include indium (In), gallium (Ga), zinc (Zn), and oxygen
(O), for example.
[0176] The atomic ratio of a sum of indium, gallium, and zinc in
metallic elements included in the source region 14, the drain
region 16, and the channel region 18 is, for example, 90% or
higher. For example, the source region 14 and the drain region 16
do not include any element that has a higher atomic ratio than any
of indium, gallium, and zinc.
[0177] The atomic ratio of a sum of indium, gallium, and zinc in
metallic elements included in the source region 14, the drain
region 16, and the channel region 18 is, for example, 90% or
higher. The atomic ratio of a sum of indium, gallium, and zinc in
elements included in the channel region 18 except oxygen, is, for
example, 90% or higher. For example, the channel region 18 does not
include any element that has a higher atomic ratio than any of
indium, gallium, and zinc, except oxygen.
[0178] The gate electrode 20 is provided so as to surround the
channel region 18. The gate electrode 20 is provided around the
channel region 18.
[0179] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example. A length (d2 in FIG. 20) of the gate electrode 20
along the third direction is equal to or larger than 20 nm and is
equal to or smaller than 100 nm, for example. The length d2 of the
gate electrode 20 along the third direction is the gate length of
the transistor 200.
[0180] The first distance d3 along the third direction between
respective portions of the source region 14 and the drain region 16
between which the surface portion 18a is sandwiched is equal to the
length d2 of the gate electrode 20 along the third direction, for
example. In other words, the length of the surface portion 18a
along the third direction is equal to the length d2 of the gate
electrode 20 along the third direction.
[0181] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example.
[0182] The gate insulating layer 22 is provided between the channel
region 18 and the gate electrode 20. The gate insulating layer 22
is provided so as to surround the channel region 18.
[0183] The gate insulating layer 22 is an oxide or an oxynitride,
for example. The gate insulating layer 22 is silicon oxide or
aluminum oxide, for example. The gate insulating layer 22 has a
thickness equal to or larger than 2 nm and is equal to or smaller
than 10 nm, for example.
[0184] The first interlayer insulating layer 26 is provided between
the source electrode 10 and the gate electrode 20. The first
interlayer insulating layer 26 is provided around the source region
14.
[0185] The first interlayer insulating layer 26 is an oxide, a
nitride, or an oxynitride, for example. The first interlayer
insulating layer 26 is silicon oxide, for example.
[0186] The second interlayer insulating layer 28 is provided
between the drain electrode 12 and the gate electrode 20. The
second interlayer insulating layer 28 is provided around the drain
region 16.
[0187] The second interlayer insulating layer 28 is an oxide, a
nitride, or an oxynitride, for example. The second interlayer
insulating layer 28 is silicon oxide, for example.
[0188] Next, an example of a semiconductor-device manufacturing
method of the second embodiment will be described.
[0189] FIGS. 23 to 34 are schematic sectional views illustrating
the semiconductor-device manufacturing method of the second
embodiment. FIGS. 23 to 34 illustrate sections corresponding to the
section illustrated in FIG. 20.
[0190] First, a first tungsten film 40, a first silicon oxide film
42, a first silicon nitride film 44, a polycrystalline silicon film
46, a second silicon nitride film 48, and a second silicon oxide
film 50 are formed sequentially in the stated order (FIG. 23). The
first tungsten film 40, the first silicon oxide film 42, the first
silicon nitride film 44, the polycrystalline silicon film 46, the
second silicon nitride film 48, and the second silicon oxide film
50 are formed by a CVD process, for example.
[0191] Subsequently, boring is performed from the surface of the
second silicon oxide film 50 to form a first opening 52 extending
to the first tungsten film 40 (FIG. 24). The first opening 52 is
formed using a lithography process and a RIE process, for
example.
[0192] Subsequently, an oxide semiconductor film 53 is buried in
the first opening 52 (FIG. 25). The oxide semiconductor film 53
includes indium (In), gallium (Ga), and zinc (Zn), for example.
[0193] Subsequently, a second tungsten film 62 is formed on the
second silicon oxide film 50 and the oxide semiconductor film 53
(FIG. 26). The second tungsten film 62 is formed by a CVD process,
for example.
[0194] Subsequently, the first silicon oxide film 42 and the second
silicon oxide film 50 are removed (FIG. 27). The first silicon
oxide film 42 and the second silicon oxide film 50 are removed by a
wet etching process, for example.
[0195] Subsequently, an exposed portion of the oxide semiconductor
film 53 is subjected to a process for reducing the resistance of
the oxide semiconductor film 53, thereby forming a first
low-resistance region 53a (FIG. 28).
[0196] The first low-resistance region 53a is formed by heat
treatment in an atmosphere including at least one predetermined
element selected from the group consisting of indium (In), silicon
(Si), and tin (Sn), for example. The heat treatment causes the
predetermined element to be introduced into the oxide semiconductor
film 53. Further, the first low-resistance region 53a is formed
through generation of an oxide vacancy by hydrogen annealing, for
example.
[0197] Subsequently, the first silicon nitride film 44 and the
second silicon nitride film 48 are removed (FIG. 29). The first
silicon nitride film 44 and the second silicon nitride film 48 are
removed by a wet etching process, for example.
[0198] Subsequently, an exposed portion of the oxide semiconductor
film 53 is subjected to a process for reducing the resistance of
the oxide semiconductor film 53, thereby forming a second
low-resistance region 53b (FIG. 30).
[0199] The second low-resistance region 53b is formed by heat
treatment in an atmosphere including at least one predetermined
element selected from the group consisting of indium (In), silicon
(Si), and tin (Sn), for example. Further, the second low-resistance
region 53b is formed through generation of an oxide vacancy by
hydrogen annealing, for example.
[0200] Subsequently, a third silicon oxide film 63 is formed so as
to cover an exposed portion of the oxide semiconductor film 53
(FIG. 31). The third silicon oxide film 63 is formed by a CVD
process, for example.
[0201] Subsequently, the polycrystalline silicon film 46 is removed
(FIG. 32). The polycrystalline silicon film 46 is removed by a wet
etching process, for example. The oxide semiconductor film 53 is
partially exposed.
[0202] Subsequently, a fourth silicon oxide film 66 is formed so as
to be in contact with the exposed portion of the oxide
semiconductor film 53 (FIG. 33). The fourth silicon oxide film 66
is formed by a CVD process, for example. The fourth silicon oxide
film 66 serves as the gate insulating layer 22.
[0203] Subsequently, a third tungsten film 68 is formed so as to be
in contact with the fourth silicon oxide film 66 (FIG. 34). The
third tungsten film 68 is formed by a CVD process, for example. The
third tungsten film 68 serves as the gate electrode 20.
[0204] By the above-described manufacturing method, the transistor
200 illustrated in FIG. 20 is formed.
[0205] In the transistor 200 of the second embodiment, a distance
(d4 in FIG. 20) between the source region 14 and the drain region
16 in a portion remote from the gate electrode 20 in the channel
region 18, i.e., in the core portion 18b, is larger than a distance
(d3 in FIG. 20) between the source region 14 and the drain region
16 in the surface portion 18a immediately below the gate electrode
20. Thus, a leakage current is unlikely to flow in a portion remote
from the gate electrode 20 in the channel region 18. Therefore, it
is easy to reduce an off-leakage current.
[0206] Further, each of the source region 14 and the drain region
16 of the transistor 200 of the second embodiment is an oxide
semiconductor with low electrical resistance. For this reason, it
is easy to reduce contact resistance between the source electrode
10 and the source region 14. For the same reasons, it is easy to
reduce contact resistance between the drain electrode 12 and the
drain region 16. Therefore, it is easy to reduce on-resistance.
[0207] The transistor 200 of the second embodiment can reduce an
off-leakage current and can reduce on-resistance as compared to the
transistor 900 of the comparative example in the first
embodiment.
[0208] FIG. 35 is a schematic sectional view of a semiconductor
device of a first modification of the second embodiment. The
semiconductor device of the first modification is a transistor
291.
[0209] The transistor 291 is different from the transistor 200 of
the second embodiment in that a part of the source region 14 and
the gate electrode 20 positionally overlap each other along the
third direction and that a part of the drain region 16 and the gate
electrode 20 positionally overlap each other along the third
direction. Thus, a distance (d3 in FIG. 35) between respective
portions of the source region 14 and the drain region 16 in the
surface portion 18a is smaller than a length (d2 in FIG. 35) of the
gate electrode 20 along the third direction. The distance d3
between respective portions of the source region 14 and the drain
region 16 in the surface portion 18a is equal to or smaller than
0.9 times the length d2 of the gate electrode 20 along the third
direction, for example.
[0210] In the transistor 291 of the first modification, the source
region 14 and the gate electrode 20 overlap each other and the
drain region 16 and the gate electrode 20 overlap each other. As a
result of this, offsets between the source region 14 and the gate
electrode 20 and between the drain region 16 and the gate electrode
20 due to variation in process, for example, are unlikely to occur.
Therefore, a transistor with stable on-resistance can be
achieved.
[0211] FIG. 36 is a schematic sectional view of a semiconductor
device of a second modification of the second embodiment. The
semiconductor device of the second modification is a transistor
292.
[0212] The transistor 292 is different from the transistor 200 of
the second embodiment in that the source region 14 and the gate
electrode 20 do not positionally overlap each other along the third
direction and in that the drain region 16 and the gate electrode 20
do not positionally overlap each other along the third direction.
Thus, a distance (d3 in FIG. 36) between respective portions of the
source region 14 and the drain region 16 in the surface portion 18a
is larger than a length (d2 in FIG. 36) of the gate electrode 20
along the third direction. The distance d3 between respective
portions of the source region 14 and the drain region 16 in the
surface portion 18a is equal to or larger than 1.1 times the length
d2 of the gate electrode 20 along the third direction.
[0213] In the transistor 292 of the second modification, the source
region 14 and the gate electrode 20, as well as the drain region 16
and the gate electrode 20, are displaced with respect to each
other. Therefore, a transistor with a further reduced off-leakage
current can be achieved.
[0214] As described above, according to the second embodiment, a
transistor that can reduce an off-leakage current and can reduce
on-resistance can be achieved.
Third Embodiment
[0215] A semiconductor device of a third embodiment includes a
first electrode, a second electrode, a ring-shaped first oxide
semiconductor region provided between the first electrode and the
second electrode, a ring-shaped second oxide semiconductor region
provided between the first oxide semiconductor region and the
second electrode, a third oxide semiconductor region at least
partly provided between the first oxide semiconductor region and
the second oxide semiconductor region, the third oxide
semiconductor region having electrical resistance higher than those
of the first oxide semiconductor region and the second oxide
semiconductor region, agate electrode surrounding the third oxide
semiconductor region, a gate insulating layer provided between the
third oxide semiconductor region and the gate electrode, a first
insulating layer provided between the first electrode and the gate
electrode, the first insulating layer including a first dielectric
having a dielectric constant higher than that of silicon oxide, and
a second insulating layer provided between the second electrode and
the gate electrode, the second insulating layer including a second
dielectric having a dielectric constant higher than that of silicon
oxide.
[0216] FIGS. 37 to 39 are schematic sectional views of the
semiconductor device of the third embodiment. FIG. 38 is a
sectional view taken along D-D' in FIG. 37. FIG. 39 is a sectional
view taken along E-E' in FIG. 37. In FIG. 37, a horizontal
direction is referred to as a first direction, a depth direction is
referred to as a second direction, and a vertical direction is
referred to as a third direction.
[0217] The semiconductor device of the third embodiment is a
transistor 300. The transistor 300 is an oxide semiconductor
transistor in which a channel is formed in an oxide semiconductor.
In the transistor 300, a gate electrode is provided so as to
surround an oxide semiconductor in which a channel is formed. The
transistor 300 is a so-called SGT. The transistor 300 is a
so-called vertical transistor.
[0218] The transistor 300 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, a core
insulating region 24, a first high-dielectric-constant insulating
layer 25, a second high-dielectric-constant insulating layer 27, a
first interlayer insulating layer 26, and a second interlayer
insulating layer 28.
[0219] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first oxide
semiconductor region. The drain region 16 is one example of the
second oxide semiconductor region. The channel region 18 is one
example of the third oxide semiconductor region. The core
insulating region 24 is one example of the insulating region. The
first high-dielectric-constant insulating layer 25 is one example
of the first insulating layer. The second high-dielectric-constant
insulating layer 27 is one example of the second insulating
layer.
[0220] The source electrode 10 is a metal or a metallic compound,
for example. The source electrode 10 is tungsten (W), for
example.
[0221] The drain electrode 12 is a metal or a metallic compound,
for example. The drain electrode 12 is tungsten (W), for
example.
[0222] The source region 14 is provided between the source
electrode 10 and the drain electrode 12. The source region 14 and
the source electrode 10 are in contact with each other. The source
region 14 and the source electrode 10 are electrically
connected.
[0223] The source region 14 is ring-shaped. The source region 14 is
ring-shaped in a plane parallel to the first direction and the
second direction. The source region 14 surrounds the core
insulating region 24. The source region 14 is in contact with the
core insulating region 24.
[0224] The source region 14 is an oxide semiconductor. The source
region 14 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O). The source region 14
is amorphous, for example.
[0225] The drain region 16 is provided between the source region 14
and the drain electrode 12. The drain region 16 is in contact with
the drain electrode 12. The drain region 16 is electrically
connected to the drain electrode 12.
[0226] The drain region 16 is ring-shaped. The drain region 16 is
ring-shaped in a plane parallel to the first direction and the
second direction. The drain region 16 surrounds the core insulating
region 24. The drain region 16 is in contact with the core
insulating region 24.
[0227] The drain region 16 is an oxide semiconductor. The drain
region 16 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O).
[0228] The drain region 16 is formed of the same oxide
semiconductor as that forming the source region 14. The drain
region 16 includes the same metallic element as that included in
the source region 14. The drain region 16 is amorphous, for
example.
[0229] The channel region 18 is provided between the source region
14 and the drain region 16. The channel region 18 is in contact
with the source region 14 and the drain region 16.
[0230] The channel region 18 is ring-shaped. The channel region 18
is ring-shaped in a plane parallel to the first direction and the
second direction. The channel region 18 surrounds the core
insulating region 24. The channel region 18 is tube-shaped, for
example.
[0231] The channel region 18 is spaced apart from the source
electrode 10. The channel region 18 is spaced apart from the drain
electrode 12.
[0232] In the channel region 18, a channel serving as a current
path during on-operation of the transistor 300 is formed. The
channel region 18 extends along a direction toward the drain
electrode 12 from the source electrode 10, that is, along the third
direction. During on-operation of the transistor 300, a current
flows along the third direction in the channel region 18.
[0233] The channel region 18 is an oxide semiconductor. The channel
region 18 includes at least one metallic element selected from the
group consisting of indium (In), gallium (Ga), zinc (Zn), aluminum
(Al), magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), and oxygen (O).
[0234] The channel region 18 is formed of the same oxide
semiconductor as that forming the source region 14 and the drain
region 16. The channel region 18 includes the same metallic element
as that included in the source region 14 and the drain region 16.
The channel region 18 is amorphous, for example.
[0235] The channel region 18 has electrical resistance higher than
the electrical resistance of the source region 14. The channel
region 18 has electrical resistance higher than the electrical
resistance of the drain region 16.
[0236] In other words, the source region 14 has electrical
resistance lower than the electrical resistance of the channel
region 18. The drain region 16 has electrical resistance lower than
the electrical resistance of the channel region 18.
[0237] The channel region 18 has a carrier concentration lower than
the carrier concentration of the source region 14. The channel
region 18 has a carrier concentration lower than the carrier
concentration of the drain region 16.
[0238] In other words, the source region 14 has a carrier
concentration higher than the carrier concentration of the channel
region 18. The drain region 16 has a carrier concentration higher
than the carrier concentration of the channel region 18.
[0239] The source region 14 and the drain region 16 include an
oxide vacancy. The channel region 18 either includes an oxide
vacancy or does not include an oxide vacancy. The concentration of
oxide vacancy in the source region 14 and the drain region 16 is
higher than the concentration of oxide vacancy in the channel
region 18.
[0240] The oxide vacancy functions as a donor that emits electrons
in an oxide semiconductor.
[0241] The source region 14, the drain region 16, and the channel
region 18 include indium (In), gallium (Ga), zinc (Zn), and oxygen
(O), for example.
[0242] The source region 14 and the drain region 16 have an oxygen
concentration lower than the oxygen concentration of the channel
region 18.
[0243] The atomic ratio of a sum of indium, gallium and zinc in
metallic elements included in the source region 14, the drain
region 16, and the channel region 18 is, for example, 90% or
higher. For example, the source region 14 and the drain region 16
do not include any element that has a higher atomic ratio than any
of indium, gallium, and zinc.
[0244] The atomic ratio of a sum of indium, gallium, and zinc in
metallic elements included in the source region 14, the drain
region 16, and the channel region 18 is, for example, 90% or
higher. The atomic ratio of a sum of indium, gallium, and zinc in
elements included in the channel region 18 except oxygen, is, for
example, 90% or higher. For example, the channel region 18 does not
include any element that has a higher atomic ratio than any of
indium, gallium, and zinc, except oxygen.
[0245] The gate electrode 20 is provided so as to surround the
channel region 18. The gate electrode 20 is provided around the
channel region 18.
[0246] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example. A length (d2 in FIG. 37) of the gate electrode 20
along the third direction is equal to or larger than 20 nm and is
equal to or smaller than 100 nm, for example. The length d2 of the
gate electrode 20 along the third direction is the gate length of
the transistor 300.
[0247] A first distance d3 along the third direction between the
source region 14 and the drain region 16 between which the channel
region 18 is sandwiched is smaller than the length d2 of the gate
electrode 20 along the third direction, for example. In other
words, a length of the channel region 18 along the third direction
is smaller than the length d2 of the gate electrode 20 along the
third direction.
[0248] The gate electrode 20 is a metal, a metallic compound, or a
semiconductor, for example. The gate electrode 20 is tungsten (W),
for example.
[0249] The gate insulating layer 22 is provided between the channel
region 18 and the gate electrode 20. The gate insulating layer 22
is provided so as to surround the channel region 18.
[0250] The gate insulating layer 22 is an oxide or an oxynitride,
for example. The gate insulating layer 22 is silicon oxide or
aluminum oxide, for example. The gate insulating layer 22 has a
thickness equal to or larger than 2 nm and is equal to or smaller
than 10 nm, for example.
[0251] The core insulating region 24 is provided between the source
electrode 10 and the drain electrode 12. The core insulating region
24 is surrounded by the source region 14, the drain region 16, and
the channel region 18. The core insulating region 24 is
cylindrical, for example. The core insulating region 24 and the
source electrode 10 are in contact with each other, for example.
The core insulating region 24 and the drain electrode 12 are in
contact with each other, for example.
[0252] The core insulating region 24 is an oxide, a nitride, or an
oxynitride, for example. The core insulating region 24 is silicon
oxide, silicon nitride, or silicon oxynitride, for example.
[0253] The first high-dielectric-constant insulating layer 25 is
provided between the source electrode 10 and the gate electrode 20.
The gate insulating layer 22 is sandwiched between the gate
electrode 20 and the first high-dielectric-constant insulating
layer 25. The gate insulating layer 22 is sandwiched between the
source electrode 10 and the first high-dielectric-constant
insulating layer 25.
[0254] The first high-dielectric-constant insulating layer 25
surrounds the source region 14. The first high-dielectric-constant
insulating layer 25 is in contact with the source region 14. The
first high-dielectric-constant insulating layer 25 is
ring-shaped.
[0255] The first high-dielectric-constant insulating layer 25
includes a first dielectric having a dielectric constant higher
than that of silicon oxide. The first dielectric is an oxide, a
nitride, or an oxynitride, for example. The first dielectric is a
metal oxide, for example. The first dielectric is hafnium oxide,
zirconium oxide, or aluminum oxide, for example. The first
dielectric is silicon nitride or silicon oxynitride, for
example.
[0256] The first dielectric is a compound having a composition
deviated from a stoichiometric composition, for example. The first
dielectric is a metal oxide including less oxygen than that in a
stoichiometric composition, for example.
[0257] The second high-dielectric-constant insulating layer 27 is
provided between the drain electrode 12 and the gate electrode 20.
The gate insulating layer 22 is sandwiched between the gate
electrode 20 and the second high-dielectric-constant insulating
layer 27. The gate insulating layer 22 is sandwiched between the
drain electrode 12 and the second high-dielectric-constant
insulating layer 27.
[0258] The second high-dielectric-constant insulating layer 27
surrounds the drain region 16. The second high-dielectric-constant
insulating layer 27 is in contact with the drain region 16. The
second high-dielectric-constant insulating layer 27 is
ring-shaped.
[0259] The second high-dielectric-constant insulating layer 27
includes a second dielectric having a dielectric constant higher
than that of silicon oxide. The second dielectric is an oxide, a
nitride, or an oxynitride, for example. The second dielectric is a
metal oxide, for example. The second dielectric is hafnium oxide,
zirconium oxide, or aluminum oxide, for example. The second
dielectric is silicon nitride or silicon oxynitride, for
example.
[0260] The second dielectric is a compound having a composition
deviated from a stoichiometric composition, for example. The second
dielectric is a metal oxide including less oxygen than that in a
stoichiometric composition, for example.
[0261] The first dielectric and the second dielectric are the same
substance, for example.
[0262] The first interlayer insulating layer 26 is provided between
the source electrode 10 and the gate electrode 20. The first
interlayer insulating layer 26 is provided around the source region
14 and the first high-dielectric-constant insulating layer 25.
[0263] The first interlayer insulating layer 26 is an oxide, a
nitride, or an oxynitride, for example. The first interlayer
insulating layer 26 is silicon oxide, for example.
[0264] The second interlayer insulating layer 28 is provided
between the drain electrode 12 and the gate electrode 20. The
second interlayer insulating layer 28 is provided around the drain
region 16 and the second high-dielectric-constant insulating layer
27.
[0265] The second interlayer insulating layer 28 is an oxide, a
nitride, or an oxynitride, for example. The second interlayer
insulating layer 28 is silicon oxide, for example.
[0266] Next, an example of a semiconductor-device manufacturing
method of the third embodiment will be described.
[0267] FIGS. 40 to 52 are schematic sectional views illustrating
the semiconductor-device manufacturing method of the third
embodiment. FIGS. 40 to 52 illustrate sections corresponding to the
section illustrated in FIG. 37.
[0268] First, a first tungsten film 40, a first silicon oxide film
42, a second tungsten film 43, a second silicon oxide film 50, and
a silicon nitride film 51 are formed sequentially in the stated
order (FIG. 40). The first tungsten film 40, the first silicon
oxide film 42, the second tungsten film 43, the second silicon
oxide film 50, and the silicon nitride film 51 are formed by a CVD
process, for example.
[0269] The first tungsten film 40 eventually serves as the source
electrode 10. A part of the first silicon oxide film 42 eventually
serves as the first interlayer insulating layer 26. A part of the
second tungsten film 43 eventually serves as the gate electrode 20.
A part of the second silicon oxide film 50 eventually serves as the
second interlayer insulating layer 28.
[0270] Subsequently, boring is performed from the surface of the
silicon nitride film 51 to forma first opening 52 extending to the
first tungsten film 40 (FIG. 41). The first opening 52 is formed
using a lithography process and a RIE process, for example.
[0271] Subsequently, the first silicon oxide film 42 and the second
silicon oxide film 50 are selectively etched from the inner face of
the first opening 52 to cause the first silicon oxide film 42 and
the second silicon oxide film 50 to recede (FIG. 42). The first
silicon oxide film 42 and the second silicon oxide film 50 are
caused to recede by a wet etching process, for example.
[0272] Subsequently, a third silicon oxide film 63 is formed so as
to cover the inner face of the first opening 52 (FIG. 43). The
third silicon oxide film 63 is formed by a CVD process, for
example. Apart of the third silicon oxide film 63 eventually serves
as the gate insulating layer 22.
[0273] Subsequently, a hafnium oxide film 65, for example, is
formed so as to cover the third silicon oxide film 63 on the inner
face of the first opening 52 (FIG. 44). The hafnium oxide film 65
is formed by a CVD process, for example.
[0274] A part of the hafnium oxide film 65 eventually serves as the
first high-dielectric-constant insulating layer 25. Another part of
the hafnium oxide film 65 eventually serves as the second
high-dielectric-constant insulating layer 27.
[0275] The hafnium oxide film 65 has a composition including less
oxygen than that in a stoichiometric composition of hafnium oxide,
for example. The hafnium oxide film 65 includes an oxygen
vacancy.
[0276] Thereafter, hydrogen annealing is performed, for example.
The hydrogen annealing increases the amount of oxygen vacancies in
the hafnium oxide film 65. The hydrogen annealing reduces the
oxygen concentration of the hafnium oxide film 65.
[0277] Subsequently, portions of the hafnium oxide film 65 on the
bottom and the inner face of the first opening 52 and above the
silicon nitride film 51 are removed. Subsequently, portions of the
third silicon oxide film 63 on the bottom of the first opening 52
and on the upper surface of the silicon nitride film 51 are removed
(FIG. 45). The portions of the hafnium oxide film 65 and the
portions of the third silicon oxide film 63 are removed using a RIE
process, for example.
[0278] Subsequently, the silicon nitride film 51 and a portion of
the third silicon oxide film 63 on a side face of the silicon
nitride film 51 are removed (FIG. 46). The silicon nitride film 51
and the portion of the third silicon oxide film 63 on a side face
of the silicon nitride film 51 are removed using a wet etching
process and a RIE process, for example.
[0279] Subsequently, an oxide semiconductor film 53 is formed in
the first opening 52 (FIG. 47). The oxide semiconductor film 53 is
formed by a CVD process, for example. The oxide semiconductor film
53 includes indium (In), gallium (Ga), and zinc (Zn), for example.
A part of the oxide semiconductor film 53 eventually serves as the
channel region 18.
[0280] Subsequently, heat treatment in a non-oxidizing atmosphere
is performed. By the heat treatment, a first
low-oxygen-concentration region 67 and a second
low-oxygen-concentration region 69 are formed (FIG. 48). The heat
treatment causes oxygen in the oxide semiconductor film 53 to be
absorbed into the hafnium oxide film 65 that has many oxygen
vacancies and thus has a low oxygen concentration. In the oxide
semiconductor film 53, a neighborhood of a region in contact with
the hafnium oxide film 65 forms the first low-oxygen-concentration
region 67 and the second low-oxygen-concentration region 69 each of
which has many oxygen vacancies and thus has a low oxygen
concentration.
[0281] The first low-oxygen-concentration region 67 eventually
serves as the source region 14. The second low-oxygen-concentration
region 69 eventually serves as the drain region 16.
[0282] The first low-oxygen-concentration region 67 and the second
low-oxygen-concentration region 69 are formed in a self-aligned
manner with respect to the second tungsten film 43. Thus, the
source region 14 and the drain region 16 are formed in a
self-aligned manner with respect to the gate electrode 20.
[0283] Subsequently, portions of the oxide semiconductor film 53 on
the bottom of the first opening 52 and on the upper portion of the
third silicon oxide film 63 are removed (FIG. 49). The portions of
the oxide semiconductor film 53 are removed using an RIE process,
for example.
[0284] Subsequently, a fourth silicon oxide film 66 is buried in
the first opening 52 (FIG. 50). The fourth silicon oxide film 66 is
formed by a CVD process, for example. Apart of the fourth silicon
oxide film 66 eventually serves as the core insulating region
24.
[0285] Subsequently, portions of the fourth silicon oxide film 66
on the second silicon oxide film 50 and on the upper portion of the
third silicon oxide film 63 are removed (FIG. 51). The portions of
the fourth silicon oxide film 66 are removed by a CMP process, for
example.
[0286] Subsequently, a third tungsten film 81 is formed on the
second silicon oxide film 50, the third silicon oxide film 63, the
second low-oxygen-concentration region 69, and the fourth silicon
oxide film 66 (FIG. 52). The third tungsten film 81 is formed by a
CVD process, for example. The third tungsten film 81 serves as the
drain electrode 12.
[0287] By the above-described manufacturing method, the transistor
300 illustrated in FIG. 37 is formed.
[0288] In the transistor 300 of the third embodiment, the core
insulating region 24 is provided inside the channel region 18. This
can reduce the thickness of the channel region 18. Therefore, it is
easy to reduce an off-leakage current.
[0289] Further, each of the source region 14 and the drain region
16 of the transistor 300 of the third embodiment is an oxide
semiconductor with low resistance. For this reason, it is easy to
reduce contact resistance between the source electrode 10 and the
source region 14. For the same reason, it is easy to reduce contact
resistance between the drain electrode 12 and the drain region 16.
Therefore, it is easy to reduce on-resistance.
[0290] The transistor 300 of the third embodiment can reduce an
off-leakage current and can reduce on-resistance as compared to the
transistor 900 of the comparative example in the first
embodiment.
[0291] Moreover, the transistor 300 of the third embodiment
includes the first high-dielectric-constant insulating layer 25 and
the second high-dielectric-constant insulating layer 27 each having
a high dielectric constant, on opposite sides of the gate electrode
20. This increases the strength of a fringing field generated from
a side face of the gate electrode 20 toward the source region 14
and the drain region 16. Thus, the carrier concentration of the
source region 14 and the drain region 16 is increased, thereby
reducing the resistance of the source region 14 and the drain
region 16. Therefore, the on-resistance of the transistor 300 is
reduced.
[0292] It is preferable that the first distance d3 along the third
direction between the source region 14 and the drain region 16
between which the channel region 18 is sandwiched is smaller than
the length d2 of the gate electrode 20 along the third direction.
In other words, it is preferable that the source region 14 and the
gate electrode 20 overlap each other and the drain region 16 and
the gate electrode 20 overlap each other. As a result of this,
offsets between the source region 14 and the gate electrode 20 and
between the drain region 16 and the gate electrode 20 due to
variation in process, for example, are unlikely to occur.
Therefore, a transistor with stable on-resistance is achieved.
[0293] FIG. 53 is a schematic sectional view of a semiconductor
device of a first modification of the third embodiment. The
semiconductor device of the first modification is a transistor
391.
[0294] The transistor 391 is different from the transistor 300 of
the third embodiment in that the source region 14 is spaced apart
from the core insulating region 24 and the drain region 16 is
spaced apart from the core insulating region 24.
[0295] The thickness of each of the source region 14 and the drain
region 16 along the first direction in the transistor 391 of the
first modification is smaller than the thickness of each of the
source region 14 and the drain region 16 along the first direction
in the transistor 300 of the third embodiment. Therefore, an
off-leakage current is further reduced.
[0296] FIG. 54 is a schematic sectional view of a semiconductor
device of a second modification of the third embodiment. The
semiconductor device of the second modification is a transistor
392.
[0297] The transistor 392 is different from the transistor 300 of
the third embodiment in that the core insulating region 24 is not
included. The thickness of each of the source region 14 and the
drain region 16 along the first direction in the transistor 392 is
smaller than the thickness of each of the source region 14 and the
drain region 16 along the first direction in the transistor 900 of
the comparative example in the first embodiment. Therefore, an
off-leakage current is reduced.
[0298] FIG. 55 is a schematic sectional view of a semiconductor
device of a third modification of the third embodiment. The
semiconductor device of the third modification is a transistor
393.
[0299] The transistor 393 is different from the transistor 300 of
the third embodiment in that the core insulating region 24, the
source region 14, and the drain region 16 are not included. The
transistor 393 does not include the source region 14 and the drain
region 16. Therefore, an off-leakage current is reduced as compared
to that in the transistor 900 of the comparative example in the
first embodiment.
[0300] As described above, according to the third embodiment, a
transistor that can reduce an off-leakage current and can reduce
on-resistance can be achieved.
Fourth Embodiment
[0301] A semiconductor memory device of a fourth embodiment
includes a first wire extending along a first direction, a second
wire extending along a second direction crossing the first
direction, and a memory cell. The memory cell includes a first
electrode electrically connected to the first wire, a second
electrode, a first metallic region provided between the first
electrode and the second electrode, the first metallic region
including at least one metallic element selected from the group
consisting of indium (In), gallium (Ga), zinc (Zn), aluminum (Al),
magnesium (Mg), manganese (Mn), titanium (Ti), tungsten (W),
molybdenum (Mo), and tin (Sn), a second metallic region provided
between the first metallic region and the second electrode, the
second metallic region including the at least one metallic element,
a semiconductor region provided between the first metallic region
and the second metallic region, the semiconductor region including
the at least one metallic element and oxygen (O), an insulating
region provided between the first metallic region and the second
metallic region, the insulating region being surrounded by the
semiconductor region, a gate electrode surrounding the
semiconductor region, the gate electrode being electrically
connected to the second wire, a gate insulating layer provided
between the semiconductor region and the gate electrode, and a
capacitor electrically connected to the second electrode. The
memory cell includes a capacitor electrically connected to the
second electrode of the semiconductor device of the first
embodiment. Hereinafter, description that would be a duplication of
the description in the first embodiment will be partly omitted.
[0302] The semiconductor memory device of the fourth embodiment is
a semiconductor memory 400. The semiconductor memory device of the
fourth embodiment is a dynamic random access memory (DRAM). The
semiconductor memory 400 uses the transistor 100 of the first
embodiment as a switching transistor of a memory cell of a
DRAM.
[0303] FIG. 56 is a block diagram of the semiconductor memory
device of the fourth embodiment.
[0304] As illustrated in FIG. 56, the semiconductor memory 400
includes a memory cell array 210, a word-line driver circuit 212, a
row decoder circuit 214, a sense amplifier circuit 215, a column
decoder circuit 217, and a control circuit 221.
[0305] FIGS. 57 and 58 are schematic sectional views of the memory
cell array of the semiconductor memory device of the fourth
embodiment. FIG. 57 is a view of a sectional plane including a
first direction and a third direction, and FIG. 58 is a view of a
sectional plane including a second direction and the third
direction. The first direction and the second direction cross each
other. The first direction and the second direction are
perpendicular to each other, for example. The third direction is
perpendicular to the first direction and the second direction. The
third direction is perpendicular to a substrate, for example.
[0306] The memory cell array 210 of the fourth embodiment includes
a three-dimensional structure in which memory cells are
three-dimensionally disposed. Each of the areas surrounded by
broken lines in FIGS. 57 and 58 represents one memory cell.
[0307] The memory cell array 210 includes a silicon substrate
250.
[0308] The memory cell array 210 includes a plurality of bit lines
BL and a plurality of word lines WL, for example, above the silicon
substrate 250. The bit lines BL extend along the first direction.
The word lines WL extend along the second direction.
[0309] The bit lines BL and the word lines WL cross each other at
right angles, for example. The memory cells are disposed in an area
where the bit lines BL and the word lines WL cross each other. The
memory cells include a first memory cell MC1 and a second memory
cell MC2. Each of the first memory cell MC1 and the second memory
cell MC2 is one example of the memory cell.
[0310] One of the bit lines BL connected to the first memory cell
MC1 and the second memory cell MC2 is a bit line BLx. The bit line
BLx is one example of the first wire. One of the word lines WL
connected to the first memory cell MC1 is a word line WLx. The word
line WLx is one example of the second wire.
[0311] One of the word lines WL connected to the second memory cell
MC2 is a word line WLy. The word line WLx is provided on one side
of the bit line BLx. The word line WLy is provided on the other
side of the bit line BLx.
[0312] The memory cell array 210 includes a plurality of plate
electrode lines PL. Each of the plate electrode lines PL is
connected to a plate electrode 72 of each memory cell.
[0313] The memory cell array 210 includes an interlayer insulating
layer 260 for electrical isolation of wires and electrodes.
[0314] The plurality of word lines WL is electrically connected to
the row decoder circuit 214. The plurality of bit lines BL is
electrically connected to the sense amplifier circuit 215.
[0315] The row decoder circuit 214 has a function of selecting one
of the word lines WL in accordance with a row address signal that
has been input. The word-line driver circuit 212 has a function of
applying a predetermined voltage to the word line WL selected by
the row decoder circuit 214.
[0316] The column decoder circuit 217 has a function of selecting
one of the bit lines BL in accordance with a column address signal
that has been input. The sense amplifier circuit 215 has a function
of applying a predetermined voltage to the bit line BL selected by
the column decoder circuit 217. The sense amplifier circuit 215
further has a function of detecting and amplifying the potential of
the bit line BL.
[0317] The control circuit 221 has a function of controlling the
word-line driver circuit 212, the row decoder circuit 214, the
sense amplifier circuit 215, the column decoder circuit 217, and
the other circuits not illustrated in the drawings.
[0318] The circuits such as the word-line driver circuit 212, the
row decoder circuit 214, the sense amplifier circuit 215, the
column decoder circuit 217, and the control circuit 221 are formed
of transistors or wiring layers not illustrated in the drawings,
for example. The transistors are formed using the silicon substrate
250, for example.
[0319] Each of the bit lines BL and the word lines WL is a metal,
for example. Each of the bit lines BL and the word lines WL is
titanium nitride, tungsten, or a stacked structure of titanium
nitride and tungsten, for example.
[0320] FIG. 59 is a schematic sectional view of the first memory
cell of the semiconductor memory device of the fourth embodiment.
FIG. 60 is a schematic sectional view of the second memory cell of
the semiconductor memory device of the fourth embodiment.
[0321] The first memory cell MC1 is provided between the silicon
substrate 250 and the bit line BLx. The bit line BLx is provided
between the silicon substrate 250 and the second memory cell
MC2.
[0322] The first memory cell MC1 is provided below the bit line
BLx. The second memory cell MC2 is provided above the bit line
BLx.
[0323] The first memory cell MC1 is provided on one side of the bit
line BLx. The second memory cell MC2 is provided on the other side
of the bit line BLx.
[0324] The second memory cell MC2 has a vertically-inverted
structure of the first memory cell MC1. Each of the first memory
cell MC1 and the second memory cell MC2 includes a transistor 100
and a capacitor 201.
[0325] The transistor 100 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, and a
core insulating region 24.
[0326] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first
metallic region. The drain region 16 is one example of the second
metallic region. The channel region 18 is one example of the
semiconductor region. The core insulating region 24 is one example
of the insulating region.
[0327] The transistor 100 has a configuration similar to that of
the transistor 100 of the first embodiment.
[0328] The capacitor 201 includes a cell electrode 71, a plate
electrode 72, and a capacitor insulating film 73. The cell
electrode 71 and the plate electrode 72 are titanium nitride, for
example. Meanwhile, the capacitor insulating film 73 has a stacked
structure of zirconium oxide, aluminum oxide, and zirconium oxide,
for example.
[0329] The cell electrode 71 of the capacitor 201 is connected to
the drain electrode 12. The plate electrode 72 is connected to the
plate electrode line PL.
[0330] The source electrode 10 is connected to the bit line BL. The
gate electrode 20 is connected to the word line WL.
[0331] Note that FIGS. 57 to 60 illustrate a case where the bit
line BL and the source electrode 10, as well as the word line WL
and the gate electrode 20, are formed of the same material
simultaneously, as an example. The bit line BL and the source
electrode 10, as well as the word line WL and the gate electrode
20, may be formed of different materials separately from each
other.
[0332] The gate electrode 20 of the first memory cell MC1 is
electrically connected to the word line WLx. Meanwhile, the gate
electrode 20 of the second memory cell MC2 is electrically
connected to the word line WLy.
[0333] According to the fourth embodiment, a semiconductor memory
with an improved memory property is achieved by using the
transistor 100 of the first embodiment as a switching transistor of
a DRAM.
Fifth Embodiment
[0334] A semiconductor memory device of a fifth embodiment includes
a first wire extending along a first direction, a second wire
extending along a second direction crossing the first direction,
and a memory cell. The memory cell includes a first electrode
electrically connected to the first wire, a second electrode, a
first oxide semiconductor region provided between the first
electrode and the second electrode, a second oxide semiconductor
region provided between the first oxide semiconductor region and
the second electrode, a third oxide semiconductor region provided
between the first oxide semiconductor region and the second oxide
semiconductor region, the third oxide semiconductor region having
electrical resistance higher than those of the first oxide
semiconductor region and the second oxide semiconductor region, and
the third oxide semiconductor region including a first portion and
a second portion surrounded by the first portion in which a first
distance between the first oxide semiconductor region and the
second oxide semiconductor region between which the first portion
is sandwiched is smaller than a second distance between the first
oxide semiconductor region and the second oxide semiconductor
region between which the second portion is sandwiched, a gate
electrode surrounding the third oxide semiconductor region, the
gate electrode being electrically connected to the second wire, a
gate insulating layer provided between the third oxide
semiconductor region and the gate electrode, and a capacitor
electrically connected to the second electrode. The memory cell
includes a capacitor electrically connected to the second electrode
of the semiconductor device of the second embodiment. Hereinafter,
description that would be a duplication of the description in the
second embodiment and the third embodiment will be partly
omitted.
[0335] The semiconductor memory device of the fifth embodiment is a
semiconductor memory. The semiconductor memory device of the fifth
embodiment is a DRAM. The semiconductor memory uses the transistor
200 of the second embodiment as a switching transistor of a memory
cell of a DRAM. The semiconductor memory device of the fifth
embodiment is a semiconductor memory in which the transistor 100 of
the semiconductor memory 400 of the fourth embodiment is replaced
by the transistor 200 of the second embodiment.
[0336] FIGS. 61 and 62 are schematic sectional views of a memory
cell array of the semiconductor memory device of the fifth
embodiment. FIG. 61 is a view of a sectional plane including a
first direction and a third direction, and FIG. 62 is a view of a
sectional plane including a second direction and the third
direction. The first direction and the second direction cross each
other. The first direction and the second direction are
perpendicular to each other, for example. The third direction is
perpendicular to the first direction and the second direction. The
third direction is perpendicular to a substrate, for example.
[0337] A memory cell array 310 of the fifth embodiment includes a
three-dimensional structure in which memory cells are
three-dimensionally disposed. Each of the areas surrounded by
broken lines in FIGS. 61 and 62 represents one memory cell.
[0338] FIG. 63 is a schematic sectional view of a first memory cell
of the semiconductor memory device of the fifth embodiment. FIG. 64
is a schematic sectional view of a second memory cell of the
semiconductor memory device of the fifth embodiment.
[0339] The first memory cell MC1 is provided between a silicon
substrate 250 and a bit line BLx. The bit line BLx is provided
between the silicon substrate 250 and the second memory cell
MC2.
[0340] The first memory cell MC1 is provided below the bit line
BLx. The second memory cell MC2 is provided above the bit line
BLx.
[0341] The first memory cell MC1 is provided on one side of the bit
line BLx. The second memory cell MC2 is provided on the other side
of the bit line BLx.
[0342] The second memory cell MC2 has a vertically-inverted
structure of the first memory cell MC1. Each of the first memory
cell MC1 and the second memory cell MC2 includes a transistor 200
and a capacitor 201.
[0343] The transistor 200 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, a first
interlayer insulating layer 26, and a second interlayer insulating
layer 28. The channel region 18 includes a surface portion 18a and
a core portion 18b.
[0344] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first oxide
semiconductor region. The drain region 16 is one example of the
second oxide semiconductor region. The channel region 18 is one
example of the third oxide semiconductor region. The surface
portion 18a is one example of the first portion. The core portion
18b is one example of the second portion.
[0345] The transistor 200 has a configuration similar to that of
the transistor 200 of the second embodiment.
[0346] The capacitor 201 includes a cell electrode 71, a plate
electrode 72, and a capacitor insulating film 73. The cell
electrode 71 and the plate electrode 72 are titanium nitride, for
example. Meanwhile, the capacitor insulating film 73 has a stacked
structure of zirconium oxide, aluminum oxide, and zirconium oxide,
for example.
[0347] The cell electrode 71 of the capacitor 201 is connected to
the drain electrode 12. The plate electrode 72 is connected to a
plate electrode line PL.
[0348] The source electrode 10 is connected to the bit line BL. The
gate electrode 20 is connected to the word line WL.
[0349] Note that FIGS. 61 to 64 illustrate a case where the bit
line BL and the source electrode 10, as well as the word line WL
and the gate electrode 20, are formed of the same material
simultaneously, as an example. The bit line BL and the source
electrode 10, as well as the word line WL and the gate electrode
20, may be formed of different materials separately from each
other.
[0350] The gate electrode 20 of the first memory cell MC1 is
electrically connected to the word line WLx. Meanwhile, the gate
electrode 20 of the second memory cell MC2 is electrically
connected to the word line WLy.
[0351] According to the fifth embodiment, a semiconductor memory
with an improved memory property is achieved by using the
transistor 200 of the second embodiment as a switching transistor
of a DRAM.
Sixth Embodiment
[0352] A semiconductor memory device of a sixth embodiment includes
a first wire extending along a first direction, a second wire
extending along a second direction crossing the first direction,
and a memory cell. The memory cell includes a first electrode
electrically connected to the first wire, a second electrode, a
ring-shaped first oxide semiconductor region provided between the
first electrode and the second electrode, a ring-shaped second
oxide semiconductor region provided between the first oxide
semiconductor region and the second electrode, a third oxide
semiconductor region at least partly provided between the first
oxide semiconductor region and the second oxide semiconductor
region, the third oxide semiconductor region having electrical
resistance higher than those of the first oxide semiconductor
region and the second oxide semiconductor region, a gate electrode
surrounding the third oxide semiconductor region, a gate insulating
layer provided between the third oxide semiconductor region and the
gate electrode, a first insulating layer provided between the first
electrode and the gate electrode, the first insulating layer
including a first dielectric having a dielectric constant higher
than that of silicon oxide, a second insulating layer provided
between the second electrode and the gate electrode, the second
insulating layer including a second dielectric having a dielectric
constant higher than that of silicon oxide, and a capacitor
electrically connected to the second electrode. The memory cell
includes a capacitor electrically connected to the second electrode
of the semiconductor device of the third embodiment. Hereinafter,
description that would be a duplication of the description in the
third embodiment and the fourth embodiment will be partly
omitted.
[0353] The semiconductor memory device of the sixth embodiment is a
semiconductor memory. The semiconductor memory device of the sixth
embodiment is a DRAM. The semiconductor memory uses the transistor
300 of the third embodiment as a switching transistor of a memory
cell of a DRAM. The semiconductor memory device of the sixth
embodiment is a semiconductor memory in which the transistor 100 of
the semiconductor memory 400 of the fourth embodiment is replaced
by the transistor 300 of the third embodiment.
[0354] FIGS. 65 and 66 are schematic sectional views of a memory
cell array of the semiconductor memory device of the sixth
embodiment. FIG. 65 is a view of a sectional plane including a
first direction and a third direction, and FIG. 66 is a view of a
sectional plane including a second direction and the third
direction. The first direction and the second direction cross each
other. The first direction and the second direction are
perpendicular to each other, for example. The third direction is
perpendicular to the first direction and the second direction.
[0355] The third direction is perpendicular to a substrate, for
example.
[0356] A memory cell array 410 of the sixth embodiment includes a
three-dimensional structure in which memory cells are
three-dimensionally disposed. Each of the areas surrounded by
broken lines in FIGS. 65 and 66 represents one memory cell.
[0357] FIG. 67 is a schematic sectional view of a first memory cell
of the semiconductor memory device of the sixth embodiment. FIG. 68
is a schematic sectional view of a second memory cell of the
semiconductor memory device of the sixth embodiment.
[0358] The first memory cell MC1 is provided between a silicon
substrate 250 and a bit line BLx. The bit line BLx is provided
between the silicon substrate 250 and the second memory cell
MC2.
[0359] The first memory cell MC1 is provided below the bit line
BLx. The second memory cell MC2 is provided above the bit line
BLx.
[0360] The first memory cell MC1 is provided on one side of the bit
line BLx. The second memory cell MC2 is provided on the other side
of the bit line BLx.
[0361] The second memory cell MC2 has a vertically-inverted
structure of the first memory cell MC1. Each of the first memory
cell MC1 and the second memory cell MC2 includes a transistor 300
and a capacitor 301.
[0362] The transistor 300 includes a source electrode 10, a drain
electrode 12, a source region 14, a drain region 16, a channel
region 18, a gate electrode 20, a gate insulating layer 22, a core
insulating region 24, a first high-dielectric-constant insulating
layer 25, a second high-dielectric-constant insulating layer 27, a
first interlayer insulating layer 26, and a second interlayer
insulating layer 28.
[0363] The source electrode 10 is one example of the first
electrode. The drain electrode 12 is one example of the second
electrode. The source region 14 is one example of the first oxide
semiconductor region. The drain region 16 is one example of the
second oxide semiconductor region. The channel region 18 is one
example of the third oxide semiconductor region. The core
insulating region 24 is one example of an insulating region. The
first high-dielectric-constant insulating layer 25 is one example
of the first insulating layer. The second high-dielectric-constant
insulating layer 27 is one example of the second insulating
layer.
[0364] The transistor 300 has a configuration similar to that of
the transistor 300 of the third embodiment.
[0365] The capacitor 301 includes a cell electrode 71, a plate
electrode 72, and a capacitor insulating film 73. The cell
electrode 71 and the plate electrode 72 are titanium nitride, for
example. Meanwhile, the capacitor insulating film 73 has a stacked
structure of zirconium oxide, aluminum oxide, and zirconium oxide,
for example.
[0366] The cell electrode 71 of the capacitor 301 is connected to
the drain electrode 12. The plate electrode 72 is connected to a
plate electrode line PL.
[0367] The source electrode 10 is connected to the bit line BL. The
gate electrode 20 is connected to the word line WL.
[0368] Note that FIGS. 65 to 68 illustrate a case where the bit
line BL and the source electrode 10, as well as the word line WL
and the gate electrode 20, are formed of the same material
simultaneously, as an example. The bit line BL and the source
electrode 10, as well as the word line WL and the gate electrode
20, may be formed of different materials separately from each
other.
[0369] The gate electrode 20 of the first memory cell MC1 is
electrically connected to the word line WLx. Meanwhile, the gate
electrode 20 of the second memory cell MC2 is electrically
connected to the word line WLy.
[0370] According to the sixth embodiment, a semiconductor memory
with an improved memory property is achieved by using the
transistor 300 of the third embodiment as a switching transistor of
a DRAM.
[0371] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the
semiconductor device and the semiconductor memory device described
herein may be embodied in a variety of other forms; furthermore,
various omissions, substitutions and changes in the form of the
devices and methods described herein may be made without departing
from the spirit of the inventions. The accompanying claims and
their equivalents are intended to cover such forms or modifications
as would fall within the scope and spirit of the inventions.
* * * * *