U.S. patent application number 14/631236 was filed with the patent office on 2015-09-10 for integrated circuit device.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. The applicant listed for this patent is KABUSHIKI KAISHA TOSHIBA. Invention is credited to Nobutoshi AOKI, Takashi IZUMIDA, Masaki KONDO, Takashi KURUSU, Tsukasa NAKAI, Hikari TAJIMA, Hiroki TOKUHIRA.
Application Number | 20150255515 14/631236 |
Document ID | / |
Family ID | 54018177 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150255515 |
Kind Code |
A1 |
NAKAI; Tsukasa ; et
al. |
September 10, 2015 |
INTEGRATED CIRCUIT DEVICE
Abstract
An integrated circuit device according to an embodiment,
includes a semiconductor member, a first electrode and a second
electrode. The semiconductor member includes a first portion of a
first conductivity type, a second portion of a second conductivity
type, and a third portion of the first conductivity type disposed
in this order along a first direction. The first electrode is
disposed on a second direction side as viewed from the
semiconductor member. The second electrode is disposed on an
opposite side of the second direction as viewed from the
semiconductor member. An end portion of the second electrode on a
first direction side is located in the first direction side rather
than that of the first electrode. An end portion of the second
electrode on an opposite side of the first direction is located in
the first direction side rather than that of the first
electrode.
Inventors: |
NAKAI; Tsukasa; (Yokkaichi
Mie, JP) ; KONDO; Masaki; (Yokkaichi Mie, JP)
; TAJIMA; Hikari; (Koganei Tokyo, JP) ; TOKUHIRA;
Hiroki; (Kawasaki Kanagawa, JP) ; IZUMIDA;
Takashi; (Yokohama Kanagawa, JP) ; KURUSU;
Takashi; (Yamato Kanagawa, JP) ; AOKI; Nobutoshi;
(Yokohama Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOSHIBA |
Tokyo |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
54018177 |
Appl. No.: |
14/631236 |
Filed: |
February 25, 2015 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61949029 |
Mar 6, 2014 |
|
|
|
Current U.S.
Class: |
365/148 ;
257/421; 257/499; 257/5; 365/158 |
Current CPC
Class: |
G11C 2013/009 20130101;
H01L 27/249 20130101; G11C 13/0026 20130101; G11C 13/0069 20130101;
G11C 13/0007 20130101; H01L 45/06 20130101; H01L 45/146 20130101;
G11C 13/0004 20130101; G11C 13/004 20130101; H01L 2924/0002
20130101; H01L 43/08 20130101; H01L 45/1226 20130101; G11C 13/003
20130101; G11C 2213/71 20130101; H01L 45/145 20130101; H01L 27/2436
20130101; H01L 27/2481 20130101; G11C 7/12 20130101; G11C 11/1673
20130101; H01L 45/04 20130101; G11C 11/1655 20130101; G11C 2013/005
20130101; G11C 2213/78 20130101; H01L 43/02 20130101; H01L 45/1253
20130101; H01L 27/228 20130101; H01L 2924/00 20130101; H01L
2924/0002 20130101; H01L 23/528 20130101; G11C 11/1659 20130101;
G11C 11/1675 20130101; H01L 27/2454 20130101; G11C 8/14 20130101;
G11C 2213/79 20130101 |
International
Class: |
H01L 27/24 20060101
H01L027/24; H01L 43/02 20060101 H01L043/02; G11C 11/16 20060101
G11C011/16; H01L 43/08 20060101 H01L043/08; G11C 13/00 20060101
G11C013/00; H01L 27/22 20060101 H01L027/22; H01L 23/528 20060101
H01L023/528 |
Claims
1. An integrated circuit device, comprising: a semiconductor member
including a first portion of a first conductivity type, a second
portion of a second conductivity type, and a third portion of the
first conductivity type disposed in this order along a first
direction; a first electrode disposed on a second direction side as
viewed from the semiconductor member, the second direction being
orthogonal to the first direction; and a second electrode disposed
on an opposite side of the second direction as viewed from the
semiconductor member, an end portion of the second electrode on a
first direction side being located in the first direction side
rather than an end portion of the first electrode on the first
direction side, and an end portion of the second electrode on an
opposite side of the first direction being located in the first
direction side rather than an end portion of the first electrode on
the opposite side of the first direction.
2. The integrated circuit device according to claim 1, wherein the
first electrode overlaps the first portion and the second portion
but does not overlap the third portion as viewed from the second
direction, and the second electrode overlaps the second portion and
the third portion but does not overlap the first portion as viewed
from the second direction.
3. The integrated circuit device according to claim 1, wherein one
portion of the first electrode and one portion of the second
electrode overlap as viewed from the second direction.
4. The integrated circuit device according to claim 1, wherein the
first electrode and the second electrode are separated in the first
direction as viewed from the second direction.
5. The integrated circuit device according to claim 4, further
comprising: a third electrode disposed at the same position as the
first electrode as viewed from the first direction and disposed at
the same position as the second electrode as viewed from the second
direction; and a fourth electrode disposed at the same position as
the second electrode as viewed from the first direction and
disposed at the same position as the first electrode as viewed from
the second direction, the insulating film being provided between
the semiconductor member and the third electrode and between the
semiconductor member and the fourth electrode.
6. An integrated circuit device, comprising: first and second
semiconductor members arranged in this order along a second
direction, each of the first and second semiconductor members
including a first portion of a first conductivity type, a second
portion of a second conductivity type, and a third portion of the
first conductivity type disposed in this order along a first
direction, the second direction being orthogonal to the first
direction; a first electrode disposed on an opposite side of the
second direction as viewed from the first semiconductor member; a
second electrode disposed between the first semiconductor member
and the second semiconductor member; and a third electrode disposed
on the second direction side as viewed from the second
semiconductor member, an end portion of the second electrode on a
first direction side being located in the first direction side
rather than an end portion of the first electrode on the first
direction side and an end portion of the third electrode on the
first direction side, and an end portion of the second electrode on
an opposite side of the first direction being located in the first
direction side rather than an end portion of the first electrode on
the opposite side of the first direction and an end portion of the
third electrode on the opposite side of the first direction.
7. The integrated circuit device according to claim 6, wherein the
first electrode and the third electrode overlap the first portion
and the second portion but do not overlap the third portion as
viewed from the second direction, and the second electrode overlaps
the second portion and the third portion but does not overlap the
first portion as viewed from the second direction.
8. The integrated circuit device according to claim 6, wherein one
portion of the first electrode and one portion of the second
electrode overlap as viewed from the second direction, and one
portion of the second electrode and one portion of the third
electrode overlap as viewed from the second direction.
9. The integrated circuit device according to claim 6, wherein the
first electrode and the second electrode are separated in the first
direction as viewed from the second direction, and the second
electrode and the third electrode are separated in the first
direction as viewed from the second direction.
10. The integrated circuit device according to claim 9, further
comprising: a fourth electrode disposed at the same position as the
first electrode as viewed from the first direction and disposed at
the same position as the second electrode as viewed from the second
direction; a fifth electrode disposed at the same position as the
second electrode as viewed from the first direction and disposed at
the same position as the first electrode as viewed from the second
direction; and a sixth electrode disposed at the same position as
the third electrode as viewed from the first direction and disposed
at the same position as the second electrode as viewed from the
second direction, the first insulating film being provided between
the first semiconductor member and the fourth electrode and between
the first semiconductor member and the fifth electrode, the second
insulating film being provided between the second semiconductor
member and the fifth electrode and between the second semiconductor
member and the sixth electrode.
11. The integrated circuit device according to claim 6, further
comprising: a first memory element connected to an end portion of
the first semiconductor member on the first direction side; a
second memory element connected to an end portion of the second
semiconductor member on the first direction side; a first
interconnect connected to an end portion of the first semiconductor
member on an opposite side of the first direction and an end
portion of the second semiconductor member on the opposite side of
the first direction; and a second interconnect connected to the
first memory element.
12. The integrated circuit device according to claim 11, wherein
the first and second memory elements are variable resistance
films.
13. The integrated circuit device according to claim 11, wherein
the first and second memory elements are phase change films.
14. The integrated circuit device according to claim 11, wherein
the first and second memory elements are magnetoresistive
elements.
15. The integrated circuit device according to claim 6, further
comprising a control circuit, the control circuit being configured
to, when selecting the first semiconductor member, apply a first
potential to the first electrode, apply a second potential to the
second electrode, and apply a third potential to the third
electrode, the third potential being lower than the first potential
and the second potential.
16. The integrated circuit device according to claim 15, wherein
the control circuit is configured to, when selecting the second
semiconductor member, apply the third potential to the first
electrode and apply the second potential or the first potential to
the second electrode and the third electrode.
17. The integrated circuit device according to claim 10, further
comprising a control circuit, the control circuit being configured
to, when selecting the first semiconductor member, apply a first
potential to the first electrode, apply a second potential to the
second electrode, apply a third potential to the third electrode,
and set the fourth to sixth electrodes to floating states, the
third potential being lower than the first potential and the second
potential.
18. The integrated circuit device according to claim 10, further
comprising a control circuit, the control circuit being configured
to, when selecting the first semiconductor member, apply a first
potential to the first electrode, apply a second potential to the
second electrode, apply a third potential to the third electrode,
and apply a fourth potential to the fourth to sixth electrodes, the
third potential being lower than the first potential and the second
potential, the fourth potential being lower than the first
potential and the second potential and higher than the third
potential.
19. The integrated circuit device according to claim 10, further
comprising a control circuit, the control circuit being configured
to, when selecting the first semiconductor member, apply a first
potential to the first electrode, apply a second potential to the
second electrode, and apply a ground potential to the third to
sixth electrodes, the first potential being higher than the ground
potential, the second potential being higher than the ground
potential.
20. The integrated circuit device according to claim 6, further
comprising: a fourth electrode disposed at the same position as the
first electrode as viewed from the first direction, the fourth
electrode overlapping the third portion in each of the first and
second semiconductor members as viewed from the second direction; a
fifth electrode disposed at the same position as the second
electrode as viewed from the first direction, the fifth electrode
overlapping the first portion in each of the first and second
semiconductor members as viewed from the second direction; and a
sixth electrode disposed at the same position as the third
electrode as viewed from the first direction, the sixth electrode
overlapping the third portion in each of the first and second
semiconductor members as viewed from the second direction, one
portion of the first electrode and one portion of the second
electrode overlapping as viewed from the second direction, and the
one portion of the second electrode and one portion of the third
electrode overlapping as viewed from the second direction.
21. The integrated circuit device according to claim 6, further
comprising: a semiconductor substrate; and a fourth electrode
disposed at the same position as the second electrode as viewed
from the first direction, the fourth electrode overlapping the
first portion in each of the first and second semiconductor members
as viewed from the second direction, a distance between the
semiconductor substrate and the first electrode being shorter than
a distance between the semiconductor substrate and the second
electrode, one portion of the first electrode and one portion of
the second electrode overlapping as viewed from the second
direction, and the one portion of the second electrode and one
portion of the third electrode overlapping as viewed from the
second direction.
22. The integrated circuit device according to claim 6, further
comprising: a semiconductor substrate provided on the opposite side
of the first direction as viewed from the first and second
semiconductor members; an active area provided on the first
direction side as viewed from the semiconductor substrate; a third
insulating film provided on the active area; a fourth electrode
provided on the first direction side as viewed from the third
insulating film; and an element-separating insulating film provided
around the active area and between the first semiconductor member
and the second semiconductor member, a distance between the
semiconductor substrate and the portion of the element-separating
insulating film disposed between the first semiconductor member and
the second semiconductor member being shorter than a distance
between the semiconductor substrate and the portion of the
element-separating insulating film provided around the active
area.
23. The integrated circuit device according to claim 6, further
comprising an interconnect provided on the opposite side of the
first direction as viewed from the first and second semiconductor
members, the interconnect connecting end portions of the first and
second semiconductor members, a distance between the interconnect
and the first electrode being shorter than a distance between the
interconnect and the second electrode, a second electrode-opposing
portion of the first semiconductor member opposing the second
electrode being finer than a portion of the first semiconductor
member disposed further on the interconnect side than is the second
electrode-opposing portion.
24. The integrated circuit device according to claim 23, wherein
the second electrode-opposing portion is finer than a first
electrode-opposing portion of the first semiconductor member
opposing the first electrode.
25. The integrated circuit device according to claim 23, wherein a
stepped portion is formed at a side surface of the first
semiconductor member on the second semiconductor member side, and a
stepped portion is not formed at a side surface of the first
semiconductor member on a side opposite to the second semiconductor
member.
26. An integrated circuit device, comprising: first and second
semiconductor members, each of the first and second semiconductor
members including a first portion of a first conductivity type, a
second portion of a second conductivity type, and a third portion
of the first conductivity type disposed in this order along a first
direction, the first and second semiconductor members being
arranged in this order along a second direction orthogonal to the
first direction; a first electrode disposed on an opposite side of
the second direction as viewed from the first semiconductor member;
a second electrode disposed between the first semiconductor member
and the second semiconductor member; a third electrode disposed on
the second direction side as viewed from the second semiconductor
member; each of the first electrode, the second electrode, and the
third electrode having: a standard work function portion; and a
high work function portion, the value of a work function of the
high work function portion being greater than the value of a work
function of the standard work function portion, in the first
electrode and the third electrode, the standard work function
portion being disposed on the first direction side as viewed from
the high work function portion, in the second electrode, the
standard work function portion being disposed on an opposite side
of the first direction as viewed from the high work function
portion, a portion of the standard work function portion of the
first electrode and a portion of the standard work function portion
of the second electrode overlapping each other as viewed from the
second direction, and a portion of the standard work function
portion of the second electrode and a portion of the standard work
function portion of the third electrode overlapping each other as
viewed from the second direction.
27. The integrated circuit device according to claim 26, wherein
the standard work function portion includes n-type silicon, and the
high work function portion includes p-type silicon.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from U.S. Provisional Patent Application 61/949,029, filed
on Mar. 6, 2014; the entire contents of which are incorporated
herein by reference.
FIELD
[0002] Embodiments described herein relate generally to an
integrated circuit device.
BACKGROUND
[0003] In recent years, a memory device has been proposed in which
memory cells are integrated two-dimensionally or
three-dimensionally. In such a memory device, the memory cells for
which the programming or reading of data is performed are selected
by selecting one interconnect of multiple interconnects provided
parallel to each other. The selection of the interconnect can be
performed by connecting a TFT (Thin Film Transistor) to the
interconnect and by switching the TFT ON/OFF.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a perspective view showing an integrated circuit
device according to a first embodiment;
[0005] FIG. 2 is a cross-sectional view showing an interconnect
selection unit of the integrated circuit device shown in FIG.
1;
[0006] FIG. 3 is a cross-sectional view showing a memory unit of
region RA of the integrated circuit device shown in FIG. 1;
[0007] FIG. 4A to FIG. 6C are cross-sectional views showing a
method for manufacturing the interconnect selection unit of the
integrated circuit device according to the first embodiment;
[0008] FIG. 7 is an example of a block diagram showing the
integrated circuit device according to the first embodiment;
[0009] FIG. 8 is a schematic cross-sectional view showing
operations and effects of the integrated circuit device according
to the first embodiment;
[0010] FIG. 9 is a schematic cross-sectional view showing an
interconnect selection unit of an integrated circuit device
according to a second embodiment;
[0011] FIG. 10 is a cross-sectional view showing an interconnect
selection unit of an integrated circuit device according to a third
embodiment;
[0012] FIGS. 11A to 11C are cross-sectional views showing a method
for manufacturing the integrated circuit device according to the
third embodiment;
[0013] FIG. 12 is a cross-sectional view showing a memory unit of
an integrated circuit device according to a forth embodiment;
[0014] FIG. 13 is a perspective view showing an integrated circuit
device according to a fifth embodiment;
[0015] FIG. 14 is a schematic cross-sectional view showing an
integrated circuit device according to a sixth embodiment;
[0016] FIG. 15A to FIG. 17D are cross-sectional views showing a
method for manufacturing the integrated circuit device according to
the sixth embodiment;
[0017] FIG. 18 is a schematic cross-sectional view showing an
integrated circuit device according to a modification of the sixth
embodiment;
[0018] FIG. 19A to FIG. 20B are cross-sectional views showing a
method for manufacturing the integrated circuit device according to
the modification of the sixth embodiment;
[0019] FIG. 21A and FIG. 21B are cross-sectional views showing a
memory cell region of an integrated circuit device according to a
seventh embodiment; and FIG. 21C is a cross-sectional view showing
a peripheral circuit region of the integrated circuit device
according to the seventh embodiment;
[0020] FIG. 22 is a cross-sectional view showing an interconnect
selection unit of an integrated circuit device according to an
eighth embodiment;
[0021] FIG. 23 is a cross-sectional view showing an interconnect
selection unit of an integrated circuit device according to a first
modification of the eighth embodiment;
[0022] FIG. 24 is a cross-sectional view showing an interconnect
selection unit of an integrated circuit device according to a
second modification of the eighth embodiment;
[0023] FIG. 25 is a cross-sectional view showing an interconnect
selection unit of an integrated circuit device according to a ninth
embodiment;
[0024] FIG. 26A to FIG. 28D are cross-sectional views showing a
method for manufacturing the integrated circuit device according to
the ninth embodiment;
[0025] FIG. 29A is an example of a graph showing a current flowing
in a selected semiconductor member and a current flowing in a
half-selected semiconductor member adjacent to the selected
semiconductor member in an integrated circuit device according to
an example of the first embodiment, where the horizontal axis is a
drain voltage, and the vertical axis is a drain current;
[0026] FIG. 29B is an example of a graph showing the current
flowing in the selected semiconductor member and the current
flowing in the half-selected semiconductor member of the integrated
circuit device according to the example of the first embodiment,
where the horizontal axis is a gate voltage, and the vertical axis
is the drain current; and
[0027] FIG. 30A and FIG. 30B are examples of graphs of the electron
concentration inside the semiconductor member; FIG. 30A shows
"selected;" and FIG. 30B shows "half-selected."
DETAILED DESCRIPTION
[0028] An integrated circuit device according to an embodiment,
includes a semiconductor member, a first electrode and a second
electrode. The semiconductor member includes a first portion of a
first conductivity type, a second portion of a second conductivity
type, and a third portion of the first conductivity type disposed
in this order along a first direction. The first electrode is
disposed on a second direction side as viewed from the
semiconductor member. The second electrode is disposed on an
opposite side of the second direction as viewed from the
semiconductor member. An end portion of the second electrode on a
first direction side is located in the first direction side rather
than that of the first electrode. An end portion of the second
electrode on an opposite side of the first direction is located in
the first direction side rather than that of the first
electrode.
[0029] Various embodiments will be described hereinafter with
reference to the accompanying drawings.
First Embodiment
[0030] First, a first embodiment will be described.
[0031] FIG. 1 is a perspective view showing an integrated circuit
device according to the embodiment.
[0032] FIG. 2 is a cross-sectional view showing an interconnect
selection unit of the integrated circuit device shown in FIG.
1.
[0033] FIG. 3 is a cross-sectional view showing the memory unit of
region RA of the integrated circuit device shown in FIG. 1.
[0034] The integrated circuit device according to the embodiment is
ReRAM (Resistance Random Access Memory).
[0035] For convenience of description hereinbelow, an XYZ
orthogonal coordinate system is employed in the specification.
[0036] As shown in FIG. 1, multiple global bit lines 10 that extend
in the X-direction are provided in the integrated circuit device 1
according to the embodiment. The multiple global bit lines 10 are
arranged periodically along the Y-direction. The global bit lines
10 are formed of, for example, the upper layer portion of a silicon
substrate partitioned by an element-separating insulator (not
shown) or are formed of polysilicon on an insulating film (not
shown) provided on a silicon substrate (not shown).
[0037] Interconnect selection units 20 are provided on the global
bit lines 10; and a memory unit 30 is provided on the interconnect
selection units 20.
[0038] As shown in FIG. 1 and FIG. 2, multiple semiconductor
members 21 are provided in the interconnect selection units 20. The
multiple semiconductor members 21 are arranged in a matrix
configuration along the X-direction and the Y-direction; and each
of the semiconductor members 21 extends in the Z-direction. Also,
the multiple semiconductor members 21 that are arranged in one
column along the X-direction have a common connection with one
global bit line 10. In each of the semiconductor members 21, an
n.sup.+-type portion 22, a p.sup.--type portion 23, and an
n.sup.+-type portion 24 are arranged in this order along the
Z-direction from the lower side, i.e., the global bit line 10 side.
The relationship between the n-type and the p-type may be
reversed.
[0039] The n.sup.+-type portions 22 and 24 are formed of, for
example, silicon into which an impurity that forms donors is
introduced. The p.sup.--type portion 23 is formed of, for example,
silicon into which an impurity that forms acceptors is introduced.
The effective impurity concentration of the p.sup.--type portion 23
is lower than the effective impurity concentrations of the
n.sup.+-type portions 22 and 24. The effective impurity
concentration refers to the concentration of the impurities
contributing to the conduction of the semiconductor material and,
for example, in the case where both an impurity that forms donors
and an impurity that forms acceptors are contained in the
semiconductor material, refers to the portion of the concentration
excluding the cancelled portion of the donors and the acceptors.
The boundary between the n.sup.+-type portion 22 and the
p.sup.--type portion 23 and the boundary between the p.sup.--type
portion 23 and the n.sup.+-type portion 24 are the positions where
the high/low relationship of the concentration reverses when
measuring the concentration profiles of the impurity that forms
donors and the impurity that forms acceptors in the semiconductor
member 21 along the Z-direction.
[0040] Gate electrodes 25a and gate electrodes 25b that extend in
the Y-direction are provided alternately between the semiconductor
members 21 in the X-direction. In the Z-direction, the gate
electrodes 25a are at the same position; and the gate electrodes
25b are at the same position. Here, the gate electrodes 25a are at
a position that is higher than the gate electrodes 25b, that is, a
position that is more distal to the global bit lines 10. The gate
electrodes 25a and 25b are formed of, for example, polysilicon.
[0041] In the Z-direction, the lengths of the gate electrodes 25a
and 25b are equal; and the lengths of the gate electrodes 25a and
25b are shorter than the length of the p.sup.--type portion 23.
Therefore, as viewed from the X-direction, the gate electrode 25a
overlaps the upper portion of the p.sup.--type portion 23 and the
lower portion of the n.sup.+-type portion 24 but does not overlap
the n.sup.+-type portion 22; and the gate electrode 25b overlaps
the upper portion of the n.sup.+-type portion 22 and the lower
portion of the p.sup.--type portion 23 but does not overlap the
n.sup.+-type portion 24.
[0042] In other words, when assuming the first and second
semiconductor members 21 adjacent to each other in the X-direction,
the first gate electrode 25b that is disposed on the side opposite
to the second semiconductor member 21 in the X-direction as viewed
from the first semiconductor member 21 overlaps the n.sup.+-type
portion 22 and the p.sup.--type portion 23 but does not overlap the
n.sup.+-type portion 24 as viewed from the X-direction. Also, the
second gate electrode 25a that is disposed between the first and
second semiconductor members 21 overlaps the p.sup.--type portion
23 and the n.sup.+-type portion 24 but does not overlap the
n.sup.+-type portion 22 as viewed from the X-direction. Also, the
third gate electrode 25b that is disposed on the side opposite to
the first semiconductor member 21 in the X-direction as viewed from
the second semiconductor member 21 overlaps the n.sup.+-type
portion 22 and the p.sup.--type portion 23 but does not overlap the
n.sup.+-type portion 24 as viewed from the X-direction.
[0043] A gate insulator film 27 made of, for example, silicon oxide
is provided between the semiconductor member 21 and the gate
electrode 25a and between the semiconductor member 21 and the gate
electrode 25b. For example, an n-channel TFT 29 is formed of the
gate electrode 25a or 25b, the gate insulator film 27, and the
semiconductor member 21 including the n.sup.+-type portion 22, the
p.sup.--type portion 23, and the n.sup.+-type portion 24.
[0044] As shown in FIG. 1 and FIG. 3, multiple local bit lines 31
are provided in the memory unit 30. The multiple local bit lines 31
are arranged in a matrix configuration along the X-direction and
the Y-direction; and each of the local bit lines 31 extends in the
Z-direction. Also, the lower ends of the local bit lines 31 are
connected to the upper ends of the semiconductor members 21. The
local bit lines 31 are formed of, for example, polysilicon.
[0045] A variable resistance film 32 that is used as the memory
elements is provided on the two side surfaces of each of the local
bit lines 31 facing the two X-direction sides. The variable
resistance film 32 is made of, for example, a metal oxide; and
when, for example, a voltage not less than a constant is applied,
the state is switched to a low resistance state by a filament F
being formed in the interior of the variable resistance film 32;
and when a voltage having the reverse polarity is applied, the
state is switched to a high resistance state by the filament F
being broken.
[0046] Multiple local word lines 33 are provided between the
variable resistance films 32 between the local bit lines 31
adjacent to each other in the X-direction. The multiple local word
lines 33 are arranged in a matrix configuration along the
X-direction and the Z-direction; and each of the local word lines
33 extends in the Y-direction. Also, the local word lines 33
contact the variable resistance films 32. In particular, the
multiple local word lines 33 arranged in one column along the
Z-direction contact common variable resistance films 32. Each of
the local word lines 33 contacts two variable resistance films 32
on the two X-direction sides.
[0047] Further, a memory cell 35 is formed of one local bit line
31, one local word line 33, and one portion of the variable
resistance film 32 interposed between the one local bit line 31 and
the one local word line 33. Accordingly, multiple memory cells 35
are connected in series to one TFT 29. In the entire memory unit
30, the multiple memory cells 35 are arranged in a
three-dimensional matrix configuration along the X-direction, the
Y-direction, and the Z-direction.
[0048] Also, in the integrated circuit device 1, an inter-layer
insulating film 11 is provided to bury the global bit lines 10, the
semiconductor members 21, the gate electrodes 25a and 25b, the gate
insulator films 27, the local bit lines 31, the variable resistance
films 32, and the local word lines 33.
[0049] A method for manufacturing the integrated circuit device
according to the embodiment will now be described with focus on the
method for manufacturing the interconnect selection unit.
[0050] FIG. 4A to FIG. 6C are cross-sectional views showing the
method for manufacturing the interconnect selection unit of the
integrated circuit device according to the embodiment.
[0051] First, as shown in FIG. 4A, an n.sup.+-type silicon layer
22a, a p.sup.--type silicon layer 23a, and an n.sup.+-type silicon
layer 24a are stacked in this order on an interconnect layer
including the multiple global bit lines 10 (referring to FIG. 1 and
FIG. 2).
[0052] Then, as shown in FIG. 4B, the stacked film made of the
n.sup.+-type silicon layer 22a, the p.sup.--type silicon layer 23a,
and the n.sup.+-type silicon layer 24a is patterned into, for
example, columnar configurations extending in the Z-direction by
dividing the stacked film into a matrix configuration along the
X-direction and the Y-direction. Thereby, the multiple
semiconductor members 21 are formed. At this time, the divided
n.sup.+-type silicon layer 22a becomes the n.sup.+-type portions
22; the divided p.sup.--type silicon layer 23a becomes the
p.sup.--type portions 23; and the divided n.sup.+-type silicon
layer 24a becomes the n.sup.+-type portions 24.
[0053] Then, as shown in FIG. 4C, liner films 61 are formed on the
side surfaces of the semiconductor members 21 by, for example,
depositing silicon nitride (SiN) by ALD (Atomic Layer Deposition)
and by subsequently performing etch-back.
[0054] Then, as shown in FIG. 5A, for example, the inter-layer
insulating film 11 that includes silicon oxide (SiO.sub.2) is
formed to bury the semiconductor members 21 and the liner films 61
by coating using PSZ (Polysilazane) (hereinbelow, called the "PSZ
method").
[0055] Then, as shown in FIG. 5B, the upper surface of the
inter-layer insulating film 11 is caused to recede to a position at
the Z-direction central portion vicinity of the p.sup.--type
portion 23 by etching the inter-layer insulating film 11. Then, for
the portions of the inter-layer insulating film 11 disposed in
every other space between the semiconductor members 21 in the
X-direction, the upper surface of the inter-layer insulating film
11 is caused to recede to a position slightly lower than the
interface between the n.sup.+-type portion 22 and the p.sup.--type
portion 23 by further etching. Thereby, a portion of the liner
films 61 is exposed.
[0056] Then, as shown in FIG. 5C, the exposed portion of the liner
films 61 is removed. Thereby, a portion of the semiconductor
members 21 is exposed. Then, for example, the gate insulator films
27 made of silicon oxide are formed on the exposed surfaces of the
semiconductor members 21 by performing thermal oxidation
treatment.
[0057] Then, as shown in FIG. 6A, a conductive film 25c made of a
conductive material such as, for example, polysilicon, etc., buries
the portions of the semiconductor members 21 and the gate insulator
films 27 protruding from the inter-layer insulating film 11.
[0058] Then, as shown in FIG. 6B, the upper surface of the
conductive film 25c is caused to recede to a position slightly
higher than the interface between the p.sup.--type portion 23 and
the n.sup.+-type portion 24 by etching the conductive film 25c.
Then, for the spaces between the semiconductor members 21 in the
X-direction where the upper surface of the inter-layer insulating
film 11 is caused to recede to the position slightly lower than the
interface between the n.sup.+-type portion 22 and the p.sup.--type
portion 23, the upper surface of the conductive film 25c is caused
to recede to a position at the Z-direction central portion vicinity
of the p.sup.--type portion 23 by further etching the conductive
film 25c. Thereby, for the conductive film 25c remaining between
the semiconductor members 21 in the X-direction, the remaining
portions that are relatively high become the gate electrodes 25a;
and the remaining portions that are relatively low become the gate
electrodes 25b.
[0059] Then, as shown in FIG. 6C, the inter-layer insulating film
11 is filled into the space where the conductive film 25c is
removed by the etching. Thus, the interconnect selection units 20
are formed such that the gate electrodes 25a and 25b are disposed
in a staggered configuration.
[0060] Then, as shown in FIG. 1 and FIG. 3, the memory unit 30 is
formed on the interconnect selection units 20. Thereby, the
integrated circuit device 1 according to the embodiment is
manufactured.
[0061] The operations and the effects of the embodiment will now be
described.
[0062] FIG. 7 is an example of a block diagram showing the
integrated circuit device according to the embodiment.
[0063] As shown in FIG. 7, the integrated circuit device 1
includes, for example, a row decoder 15 that drives the local word
lines 33 disposed in the memory unit 30, and sense amplifiers 17
that are connected to the global bit lines 10. The sense amplifiers
17 discriminate the data read from the memory cells 35 and can
temporarily store the data. Also, the integrated circuit device 1
includes a control circuit 13 and an interface circuit 19. The
control circuit 13 programs information to the memory cells 35 or
reads information from the memory cells 35 via the row decoder 15
and the sense amplifiers 17 based on instructions input from the
outside via the interface circuit 19.
[0064] For example, the control circuit 13 selects one of the
multiple global bit lines 10 via the sense amplifier 17. Also, the
control circuit 13 controls the semiconductor members 21 to select
one of the multiple local bit lines 31 provided on the selected
global bit line 10. Specifically, the local bit line 31 to be
selected and the selected global bit line 10 are electrically
connected by applying an ON potential to the gate electrode 25 of
the semiconductor member 21 provided between the local bit line 31
to be selected and the selected global bit line 10 to switch the
semiconductor member 21 ON. The details of this operation are
described below.
[0065] Also, by designating one of the multiple local word lines
33, the control circuit 13 selects one of the multiple memory cells
35 provided between the selected local bit line 31 and the local
word line 33.
[0066] For example, in the case where the information recorded in
the memory cell 35 is read, the control circuit 13 applies a
prescribed read-out voltage between the selected local word line 33
and the selected global bit line 10 and senses the current flowing
in the selected global bit line 10 by the sense amplifier 17. Then,
the information that is recorded in the memory cell 35 is
designated based on the output from the sense amplifier 17; and the
information is output via the interface circuit 19. Also, in the
case where information is programmed to the memory cell 35, or in
the case where information that is recorded in the memory cell is
erased, the memory cell is caused to transition from a first state
to a second state or reversely by applying a prescribed
programming, reading, or erasing voltage between the selected local
word line 33 and the selected global bit line 10.
[0067] FIG. 8 is a schematic cross-sectional view showing the
operations and the effects of the integrated circuit device
according to the embodiment.
[0068] The operation of the control circuit 13 selecting the
semiconductor member 21 will now be described in detail.
[0069] In the integrated circuit device 1 according to the
embodiment as shown in FIG. 8, the case is described where one
semiconductor member 21 is to be switched to the ON state, and the
other semiconductor members 21 are to be switched to the OFF state.
Hereinbelow, the semiconductor member 21 to be switched to the ON
state is called a "selected member 21a." Also, the semiconductor
members 21 that are among the semiconductor members 21 to be
switched to the OFF state and are disposed to be adjacent to the
selected member 21a on two sides are called a "half-selected member
21b" and a "half-selected member 21c"; and the other semiconductor
members 21 are called the "unselected members."
[0070] In such a case, the control circuit 13 applies an ON
potential (e.g., 3 V) to the gate electrode 25a and the gate
electrode 25b disposed on the two sides of the selected member 21a
and applies an OFF potential (e.g., 0 V) to the other gate
electrodes 25a and gate electrodes 25b. Thereby, in the upper
portion of the p.sup.--type portion 23 of the selected member 21a,
an inversion layer Ru is formed in the portion on the gate
electrode 25a side by the effect of the gate electrode 25a; and in
the lower portion of the p.sup.--type portion 23, an inversion
layer RI is formed in the portion on the gate electrode 25b side by
the effect of the gate electrode 25b. If the selected member 21a is
sufficiently fine, the inversion layer Ru of the upper portion and
the inversion layer RI of the lower portion are connected to each
other; and a continuous current path is formed inside the
p.sup.--type portion 23. As a result, the selected member 21a is
switched to the ON state.
[0071] Conversely, for half-selected member 21b that is positioned
such that the gate electrode 25a is interposed as viewed from the
selected member 21a, the inversion layer Ru is formed in the upper
portion of the p.sup.--type portion 23 because the upper portion of
the p.sup.--type portion 23 opposes the gate electrode 25a to which
the ON potential (e.g., 3 V) is applied; but the inversion layer is
not formed in the lower portion of the p.sup.--type portion 23
because the lower portion of the p.sup.--type portion 23 opposes
the gate electrode 25b to which the OFF potential (e.g., 0 V) is
applied. Therefore, the half-selected member 21b as an entirety is
in the OFF state.
[0072] Also, for half-selected member 21c that is positioned such
that the gate electrode 25b is interposed as viewed from the
selected member 21a, the inversion layer RI is formed in the lower
portion of the p.sup.--type portion 23 because the lower portion of
the p.sup.--type portion 23 opposes the gate electrode 25b to which
the ON potential is applied; but the inversion layer is not formed
in the upper portion of the p.sup.--type portion 23 because the
upper portion of the p.sup.--type portion 23 opposes the gate
electrode 25a to which the OFF potential is applied. Therefore,
half-selected member 21c as an entirety is in the OFF state.
[0073] Further, for the unselected members 21 other than the
half-selected member 21b and 21c, the inversion layer is not formed
in the p.sup.--type portion 23 and the state is the OFF state
because the OFF potential (e.g., 0 V) is applied to the gate
electrodes 25a and 25b disposed on the two sides of the unselected
members 21.
[0074] Thus, according to the embodiment, by disposing the gate
electrodes 25a and 25b arranged along the X-direction in a zigzag
configuration displaced to oscillate along the Z-direction, for the
half-selected members 21b and 21c adjacent to the selected member
21a on two sides, an inversion layer that continuously links the
n.sup.+-type portion 22 and the n.sup.+-type portion 24 can be
prevented from forming; and the half-selected members 21b and 21c
can be reliably set to the OFF state. As a result, the ratio
between the ON current and the OFF current in the semiconductor
member 21 can be high; and the operations of the integrated circuit
device are stabilized. Also, because it is sufficient for one
selected from gate electrodes 25a and 25b to be provided between
the semiconductor members 21, higher integration is easy. In other
words, according to the embodiment, an integrated circuit device
having high integration and stable operations can be realized.
Second Embodiment
[0075] A second embodiment will now be described.
[0076] FIG. 9 is a schematic cross-sectional view showing the
interconnect selection unit of the integrated circuit device
according to the embodiment.
[0077] As shown in FIG. 9, the integrated circuit device 2
according to the embodiment differs from the integrated circuit
device 1 (referring to FIG. 1 to FIG. 3) according to the first
embodiment described above in that the lower portion of the gate
electrode 25a and the upper portion of the gate electrode 25b
overlap as viewed from the X-direction.
[0078] The integrated circuit device 2 according to the embodiment
can be manufactured by adjusting the etching amount of the
inter-layer insulating film 11 in the process shown in FIG. 5B and
by adjusting the etching amount of the conductive film 25c in the
process shown in FIG. 6B.
[0079] In the embodiment, because the lower portion of the gate
electrode 25a and the upper portion of the gate electrode 25b
overlap as viewed from the X-direction, the formation regions of
the inversion layers Ru and R1 in the selected member 21a overlap
each other in the Z-direction. As a result, the coupling between
the inversion layer Ru and the inversion layer RI becomes stronger;
and the ON current flowing in the selected member 21a can be
increased even more.
[0080] Otherwise, the configuration, the operations, and the
effects of the embodiment are similar to those of the first
embodiment described above.
Third Embodiment
[0081] A third embodiment will now be described.
[0082] FIG. 10 is a cross-sectional view showing the interconnect
selection unit of the integrated circuit device according to the
embodiment.
[0083] As shown in FIG. 10, in addition to the configuration of the
integrated circuit device 1 (referring to FIG. 1 to FIG. 3)
according to the first embodiment described above, dummy electrodes
25d and 25e are provided in the integrated circuit device 3
according to the embodiment. The dummy electrodes 25d and 25e are
disposed at positions to supplement the zigzag arrangement of the
gate electrodes 25a and 25b oscillating in the Z-direction. In
other words, the dummy electrode 25d is disposed at the same
position as the gate electrode 25b as viewed from the Z-direction
and is disposed at the same position as the gate electrode 25a as
viewed from the X-direction. Also, the dummy electrode 25e is
disposed at the same position as the gate electrode 25a as viewed
from the Z-direction and is disposed at the same position as the
gate electrode 25b as viewed from the X-direction. Also, the gate
insulator film 27 is provided between the semiconductor members 21
and the dummy electrodes 25d and between the semiconductor members
21 and the dummy electrodes 25e. Hereinbelow, the gate electrodes
25a and 25b and the dummy electrodes 25d and 25e also are generally
called the "gate electrode 25." This is similar for the other
embodiments described below as well.
[0084] A method for manufacturing the integrated circuit device
according to the embodiment will now be described.
[0085] FIGS. 11A to 11C are cross-sectional views showing the
method for manufacturing the integrated circuit device according to
the embodiment.
[0086] First, the processes shown in FIG. 4A to FIG. 5A are
implemented.
[0087] Then, as shown in FIG. 11A, the upper surface of the
inter-layer insulating film 11 is caused to recede to a position
slightly lower than the interface between the n.sup.+-type portion
22 and the p.sup.--type portion 23 by performing etch-back of the
inter-layer insulating film 11.
[0088] Then, as shown in FIG. 11B, the gap after the inter-layer
insulating film 11 is removed is filled with the conductive film
25c made of a conductive material such as, for example,
polysilicon, etc. Then, the upper surface of the conductive film
25c is caused to recede to a position slightly lower than the
Z-direction center of the p.sup.--type portion 23 by performing
etching of the conductive film 25c. Then, an inter-layer insulating
film 11c is deposited; and the upper surface of the inter-layer
insulating film 11c is caused to recede to a position slightly
higher than the Z-direction center of the p.sup.--type portion 23
by performing etch-back.
[0089] Then, as shown in FIG. 11C, a conductive film 25f is
deposited; and the upper surface of the conductive film 25f is
caused to recede to a position at the vicinity of the interface
between the n.sup.+-type portion 24 and the p.sup.--type portion 23
by performing etch-back. Thus, the integrated circuit device 3
according to the embodiment is manufactured.
[0090] In the embodiment, similarly to the first embodiment
described above, one of the semiconductor members 21 is switched to
the ON state by selecting the potentials of the gate electrodes 25a
and 25b; and the other semiconductor members 21 are switched to the
OFF state. At this time, the dummy electrodes 25d and 25e are in
floating states or have a constant potential, for example, a
potential between the ON potential and the OFF potential.
[0091] According to the embodiment, by disposing the dummy
electrodes 25d and 25e to supplement the zigzag arrangement of the
gate electrodes 25a and 25b, the gate electrode 25b and the dummy
electrode 25e can be formed simultaneously; and the gate electrode
25a and the dummy electrode 25d can be formed simultaneously. As a
result, compared to the first embodiment described above, the
number of processes for forming the interconnect selection units 20
can be reduced.
[0092] Otherwise, the configuration, the operations, and the
effects of the embodiment are similar to those of the first
embodiment described above.
Fourth Embodiment
[0093] A fourth embodiment will now be described.
[0094] FIG. 12 is a cross-sectional view showing the memory unit of
the integrated circuit device according to the embodiment.
[0095] FIG. 12 is a cross-sectional view corresponding to region RA
of FIG. 1.
[0096] As shown in FIG. 12, the integrated circuit device 4
according to the embodiment differs from the integrated circuit
device 1 (referring to FIG. 1 to FIG. 3) according to the first
embodiment described above in that the integrated circuit device 4
is PRAM (Phase Random Access Memory).
[0097] Namely, in a memory unit 30a of the integrated circuit
device 4, a phase change film 42 is provided as the memory elements
on the two side surfaces of each of the local bit lines 31 facing
the two X-direction sides. The phase change film 42 is a film in
which the crystalline phase changes between a phase 43a and a phase
43b according to the voltage or current that is applied; and when
the crystalline phase changes, the electrical resistance value of
that portion changes. Then, the memory cell is formed of one local
bit line 31, one local word line 33, and one portion of the phase
change film 42 interposed between the one local bit line 31 and the
one local word line 33.
[0098] Otherwise, the configuration, the manufacturing method, the
operations, and the effects of the embodiment are similar to those
of the first embodiment described above.
Fifth Embodiment
[0099] A fifth embodiment will now be described.
[0100] FIG. 13 is a perspective view showing an integrated circuit
device according to the embodiment.
[0101] As shown in FIG. 13, the integrated circuit device 5
according to the embodiment is MRAM (Magneto resistive Random
Access Memory).
[0102] The multiple local source lines 57 are provided in the
integrated circuit device 5 by patterning the upper layer portion
of a monocrystalline silicon substrate 12. The multiple local
source lines 57 are arranged periodically along the Y-direction;
and each of the local source lines 57 extends in the X-direction.
Similarly to normal element separation, the local source lines 57
are electrically isolated from each other by STI (Shallow Trench
Isolation), a burying insulation film, an impurity concentration
profile, etc. The multiple local source lines 57 may be combined
into one. Similar to the first embodiment described above, the
interconnect selection units 20 are provided on the interconnect
layer including the multiple local source lines 57. In the
embodiment, the channels of the interconnect selection units 20 are
formed of monocrystalline silicon because the channels are formed
by directly patterning the silicon substrate 12. Therefore,
compared to the case where the channels are formed of polysilicon,
the ON current can be increased.
[0103] Also, in the integrated circuit device 5, a memory unit 30b
is provided on the interconnect selection units 20. In the memory
unit 30b, a MTJ (Magnetic Tunnel Junction) element 55 is provided
as a memory element on each of the semiconductor members 21. The
MTJ element 55 is one type of magnetoresistive element. In the MTJ
element 55, a fixed layer 51 made of a perpendicular magnetization
film that is connected to the semiconductor member 21 and has a
fixed magnetization direction, an insulating layer 52, and a memory
layer 53 made of a perpendicular magnetization film that has a
variable magnetization direction are stacked in this order from the
lower side. Local bit lines 56 that extend in the X-direction are
provided on the MTJ elements 55. The local bit lines 56 are
disposed in the regions directly above the local source lines 57.
The local bit line 56 has a common connection with the memory
layers 53 of the multiple MTJ elements 55 arranged in one column
along the X-direction.
[0104] Otherwise, the configuration, the manufacturing method, the
operations, and the effects of the embodiment are similar to those
of the first embodiment described above.
Sixth Embodiment
[0105] A sixth embodiment will now be described.
[0106] FIG. 14 is a schematic cross-sectional view showing the
integrated circuit device according to the embodiment.
[0107] The embodiment is an example in which the second embodiment
(referring to FIG. 9), the third embodiment (referring to FIG. 10),
and the fifth embodiment (referring to FIG. 13) that are described
above are combined.
[0108] Namely, as shown in FIG. 14, the integrated circuit device 6
according to the embodiment is MRAM. Also, the integrated circuit
device 6 differs from the integrated circuit device 3 according to
the third embodiment described above (referring to FIG. 10) in that
the gate electrodes 25a and 25b are longer than the dummy
electrodes 25d and 25e in the Z-direction. When viewed from the
X-direction, the lower portion of the gate electrode 25a overlaps
the upper portion of the gate electrode 25b; but the dummy
electrode 25d and the dummy electrode 25e are separated from each
other. The ON potential (e.g., 3 V) or the OFF potential (e.g., 0
V) is applied to the gate electrodes 25a and 25b. Also, a constant
potential, for example, the OFF potential (0 V) is applied to the
dummy electrodes 25d and 25e.
[0109] A method for manufacturing the integrated circuit device
according to the embodiment will now be described.
[0110] FIG. 15A to FIG. 17D are cross-sectional views showing the
method for manufacturing the integrated circuit device according to
the embodiment.
[0111] First, as shown in FIG. 15A, by patterning the upper layer
portion of the silicon substrate 12, multiple local source lines 57
are formed; and the semiconductor members 21 are multiply formed on
each of the local source lines 57 in columnar configurations in
which the n.sup.+-type portion 22, the p.sup.--type portion 23, and
the n.sup.+-type portion 24 are stacked in this order. Then, for
example, silicon nitride films 62 are formed on the side surfaces
of the semiconductor members 21 by ALD. Then, for example, an
insulating film 63a that includes silicon oxide is filled by a PSZ
method, etc., between the pillars formed of the semiconductor
members 21 and the silicon nitride films 62.
[0112] Then, as shown in FIG. 15B, the upper portions of the
semiconductor members 21 and the upper portions of the silicon
nitride films 62 are caused to protrude from the upper surface of
the insulating film 63a by causing the upper surface of the
insulating film 63a to recede by performing etch-back of the
insulating film 63a.
[0113] Then, as shown in FIG. 15C, the upper portions of the
semiconductor members 21 are exposed by removing the exposed
portions of the silicon nitride films 62. Then, thermal oxide films
64 are formed on the surfaces of the upper portions of the
semiconductor members 21 by performing thermal oxidation
treatment.
[0114] Then, as shown in FIG. 15D, an n-type polysilicon film 65a
is deposited on the entire surface. Then, etch-back of the n-type
polysilicon film 65a is performed using the thermal oxide films 64
as a stopper.
[0115] Then, as shown in FIG. 16A, a mask film 66a is formed to
cover every other region of the regions between the semiconductor
members 21 arranged along the X-direction. Then, the upper surface
of the n-type polysilicon film 65a is caused to recede in every
other region of the regions between the semiconductor members 21 by
performing etching using the mask film 66a as a mask. Subsequently,
the mask film 66a is removed.
[0116] Then, as shown in FIG. 16B, for example, an insulating film
63b that includes silicon oxide is formed using a PSZ method; and
etch-back is performed so that the insulating film 63b remains on
the portion of the n-type polysilicon film 65a having the receded
upper surface. At this time, the upper surface of the insulating
film 63b is positioned lower than the upper surface of the portion
of the n-type polysilicon film 65a that was covered with the mask
film 66a.
[0117] Then, as shown in FIG. 16C, an n-type polysilicon film 65b
is deposited on the entire surface. Then, etch-back of the n-type
polysilicon film 65b is performed using the thermal oxide films 64
as a stopper.
[0118] Then, as shown in FIG. 16D, a mask film 66b is formed in the
regions where the mask film 66a was not disposed in the process
shown in FIG. 16A; and the upper surface of the n-type polysilicon
film 65a is caused to recede in the regions not covered with the
mask film 66b by performing etching using the mask film 66b as a
mask. At this time, the upper surface of the n-type polysilicon
film 65a in this region is caused to be lower than the upper
surface of the n-type polysilicon film 65a that was caused to
recede in the process shown in FIG. 16A. Then, an insulating film
63c is formed on the exposed surface of the n-type polysilicon film
65a by forming silicon oxide using oxidation treatment or a PSZ
method. Subsequently, the mask film 66b is removed.
[0119] Then, as shown in FIG. 17A, an n-type polysilicon film 65c
is deposited on the entire surface. Then, etch-back of the n-type
polysilicon film 65c is performed using the thermal oxide films 64
as a stopper.
[0120] Then, as shown in FIG. 17B, the upper surfaces of the n-type
polysilicon films 65b and 65c are caused to recede and the upper
portions of the semiconductor members 21 and the upper portions of
the thermal oxide films 64 are caused to protrude from the upper
surfaces of the n-type polysilicon films 65b and 65c by performing
etch-back of the n-type polysilicon films 65b and 65c.
[0121] Then, as shown in FIG. 17C, for example, an insulating film
63d that includes silicon oxide is formed on the n-type polysilicon
films 65a and 65b by depositing an insulator using a PSZ method and
by performing etch-back using the thermal oxide films 64 as a
stopper.
[0122] Then, as shown in FIG. 17D, the portions of the thermal
oxide films 64 disposed on the upper surfaces of the semiconductor
members 21 are removed. Thereby, the upper surfaces of the
semiconductor members 21 are exposed.
[0123] Thus, the gate electrodes 25 that are made of n-type
polysilicon and have two levels are formed. Thereafter, the
integrated circuit device 6 is manufactured by normal methods.
[0124] Effects of the embodiment will now be described.
[0125] According to the embodiment, similarly to the second
embodiment described above, because the formation region of the
inversion layer Ru and the formation region of the inversion layer
RI overlap in a wide surface area in the selected member 21a, a
bottleneck of the current between the inversion layer Ru and the
inversion layer RI is relaxed; and the ON current increases. On the
other hand, by applying the OFF potential to the dummy electrodes
25d and 25e, the portions of the semiconductor member 21 opposing
the dummy electrodes 25d and 25e are actively set to the
nonconducting state. Thereby, the half-selected members 21b and 21c
disposed to be adjacent to the selected member 21a on two sides can
be reliably set to the OFF state. As a result, the ratio of the ON
current and the OFF current in the semiconductor member 21 can be
high; and the operations of the integrated circuit device are
stabilized. Although the effect of reducing the OFF current is
weaker, the dummy electrodes 25d and 25e may be in a floating
state.
[0126] Otherwise, the configuration, the manufacturing method, the
operations, and the effects of the embodiment are similar to those
of the fifth embodiment described above.
Modification of Sixth Embodiment
[0127] A modification of the sixth embodiment will now be
described.
[0128] FIG. 18 is a schematic cross-sectional view showing the
integrated circuit device according to the modification. As shown
in FIG. 18, the integrated circuit device 6a according to the
modification differs from the integrated circuit device 6 according
to the sixth embodiment (referring to FIG. 14) in that the dummy
electrode 25d (referring to FIG. 14) is not provided. The dummy
electrode 25e is provided. The distance between the silicon
substrate 12 (referring to FIG. 13) and the lower end of the gate
electrode 25b is shorter than the distance between the silicon
substrate 12 and the lower end of the gate electrode 25a; and the
distance between the silicon substrate 12 and the upper end of the
gate electrode 25b is longer than the distance between the silicon
substrate 12 and the lower end of the gate electrode 25a. Thereby,
as viewed from the X-direction, the lower portion of the gate
electrode 25a of the upper level and the upper portion of the gate
electrode 25b of the lower level overlap.
[0129] A method for manufacturing the integrated circuit device
according to the modification will now be described.
[0130] FIG. 19A to FIG. 20B are cross-sectional views showing the
method for manufacturing the integrated circuit device according to
the modification.
[0131] First, processes shown in FIG. 15A to FIG. 16A are
implemented.
[0132] Then, as shown in FIG. 19A, for example, the insulating film
63b is formed by a PSZ method; and etch-back is performed using the
thermal oxide films 64 as a mask so that the insulating film 63b
remains on the portion of the n-type polysilicon film 65a having
the receded upper surface. At this time, in the Z-direction, the
position of the upper surface of the insulating film 63b is
substantially the same as the position of the upper surface of the
portion of the n-type polysilicon film 65a covered with the mask
film 66a.
[0133] Then, as shown in FIG. 19B, the mask film 66b is formed in
the regions where the mask film 66a was not disposed in the process
shown in FIG. 16A; and etching is performed using the mask film 66b
as a mask so that the upper surface of the n-type polysilicon film
65a recedes in the regions not covered with the mask film 66b. At
this time, the upper surface of the n-type polysilicon film 65a in
this region is caused to be lower than the upper surface of the
n-type polysilicon film 65a that receded in the process shown in
FIG. 16A. Then, the insulating film 63c is formed on the exposed
surface of the n-type polysilicon film 65a by forming an insulating
film using oxidation treatment or a PSZ method. Subsequently, the
mask film 66b is removed.
[0134] Then, as shown in FIG. 19C, the n-type polysilicon film 65c
is deposited on the entire surface. Then, etch-back of the n-type
polysilicon film 65c is performed using the thermal oxide films 64
as a stopper.
[0135] Then, as shown in FIG. 19D, the upper portions of the
semiconductor members 21, the upper portions of the thermal oxide
films 64, and the upper portion of the insulating film 63b are
caused to protrude from the upper surface of the n-type polysilicon
film 65c by causing the upper surface of the n-type polysilicon
film 65c to recede by performing etch-back of the n-type
polysilicon film 65c.
[0136] Then, as shown in FIG. 20A, for example, the insulating film
63d is formed on the n-type polysilicon films 65a and 65c by
depositing an insulator by a PSZ method and by performing etch-back
using the thermal oxide films 64 as a stopper.
[0137] Then, as shown in FIG. 20B, the portions of the thermal
oxide films 64 disposed on the upper surfaces of the semiconductor
members 21 are removed. Thereby, the upper surfaces of the
semiconductor members 21 are exposed.
[0138] Thereafter, the integrated circuit device 6a is manufactured
by normal methods.
[0139] Effects of the modification will now be described.
[0140] According to the modification, it is no longer necessary to
form the n-type polysilicon film 65b because the dummy electrode
25d is not disposed above the gate electrode 25b. In other words,
it is sufficient to perform the depositing of the n-type
polysilicon film twice. Also, it is no longer necessary to control
the configuration of the dummy electrode 25d. For these reasons,
compared to the sixth embodiment, the manufacturing processes of
the modification are simple. Otherwise, the configuration, the
manufacturing method, the operations, and the effects of the
modification are similar to those of the sixth embodiment described
above.
Seventh Embodiment
[0141] A seventh embodiment will now be described.
[0142] FIG. 21A and FIG. 21B are cross-sectional views showing the
memory cell region of the integrated circuit device according to
the embodiment; and FIG. 21C is a cross-sectional view showing the
peripheral circuit region of the integrated circuit device
according to the embodiment. The Z-direction positions are aligned
between FIG. 21A to FIG. 21C.
[0143] In the integrated circuit device 7 according to the
embodiment as shown in FIG. 21A to FIG. 21C, the memory cell region
Rm that includes the interconnect selection unit 20 and the memory
unit 30b (referring to FIG. 13) is provided; and the peripheral
circuit region Rc in which the peripheral circuit is formed is
provided.
[0144] In the memory cell region Rm as shown in FIG. 21A and FIG.
21B, the upper layer portion of the silicon substrate 12 is
patterned to form the local source lines 57 and the semiconductor
members 21; the local source lines 57 are electrically isolated
from each other by a STI 71; and the lower portions of the
semiconductor members 21 are electrically isolated from each other
by the STI 71. Also, the upper portions of the semiconductor
members 21 are separated from each other by the inter-layer
insulating film 11. Further, the gate insulator film 27 is provided
between the local source line 57 and the gate electrode 25.
Similarly to the third embodiment described above (referring to
FIG. 10), some of the gate electrodes 25 may be dummy electrodes to
which a constant potential is applied. This is similar for the
other embodiments described below as well.
[0145] In the peripheral circuit region Rc as shown in FIG. 21C, an
active area 72 is provided in the upper layer portion of the
silicon substrate 12. The active area 72 is electrically isolated
from the surroundings by the STI 71 filled into the upper layer
portion of the silicon substrate 12. Also, for example, a gate
insulator film 73 that is made of silicon oxide is provided on the
active area 72; and, for example, a gate electrode 74 that is made
of polysilicon is provided on the gate insulator film 73.
[0146] Thus, in the memory cell region Rm, the STI 71 is disposed
between the lower portions of the semiconductor members 21; and in
the peripheral circuit region Rc, the STI 71 is disposed around the
active area 72. Then, a lowermost surface 71a of the STI 71 in the
memory cell region Rm is positioned lower than a lowermost surface
71b of the STI 71 in the peripheral circuit region Rc. In other
words, the upper portion of the silicon substrate 12 is carved out
over the entire memory cell region Rm.
[0147] According to the embodiment, by setting the lowermost
surface 71a of the STI 71 in the memory cell region Rm to be lower
than the lowermost surface 71b of the STI 71 in the peripheral
circuit region Rc, the upper layer portion of the silicon substrate
12 in the memory cell region Rm is selectively removed to form the
local source lines 57 and the semiconductor members 21 to be
sufficiently thick; while in the peripheral circuit region Rc, the
formation of the STI 71 for partitioning the active area 72 can
avoid being excessively deep. As a result, in the memory cell
region Rm, the local source lines 57 are formed to be sufficiently
thick; and the resistance of the local source lines 57 can be
reduced. On the other hand, in the peripheral circuit region Rc,
the volume of the STI 71 is prevented from becoming excessively
large; and cracks that occur in the STI 71 can be suppressed.
[0148] Otherwise, the configuration, the manufacturing method, the
operations, and the effects of the embodiment are similar to those
of the fifth embodiment described above. Although an example is
illustrated in the embodiment in which two gate electrodes 25 are
provided, only one gate electrode may be provided.
Eighth Embodiment
[0149] An eighth embodiment will now be described.
[0150] FIG. 22 is a cross-sectional view showing the interconnect
selection unit of the integrated circuit device according to the
embodiment.
[0151] As shown in FIG. 22, the integrated circuit device 8
according to the embodiment differs from the integrated circuit
device 5 according to the fifth embodiment described above
(referring to FIG. 13) in that a lower portion 211 of the
semiconductor member 21 is wider than an upper portion 21u of the
semiconductor member 21. Therefore, a stepped portion 21s is formed
at the side surfaces of the semiconductor member 21 facing two
X-direction sides between the lower portion 211 and the upper
portion 21u of the semiconductor member 21. The upper portion 21u
includes a portion opposing the two, i.e., upper and lower, levels
of the gate electrodes 25.
[0152] According to the embodiment, by setting the lower portion
211 of the semiconductor member 21 to be relatively wide, the
source resistance of the semiconductor member 21 linking the local
source line 57 to the channel can be reduced. On the other hand, by
setting the upper portion 21u of the semiconductor member 21 to be
relatively fine, the controllability by the gate electrode 25 of
the upper portion 21u is stronger; and the OFF current can be
suppressed. Thereby, the difference between the ON current and the
OFF current can be large. Otherwise, the configuration, the
manufacturing method, and the effects of the embodiment are similar
to those of the fifth embodiment described above.
First Modification of Eighth Embodiment
[0153] A first modification of the eighth embodiment will now be
described.
[0154] FIG. 23 is a cross-sectional view showing the interconnect
selection unit of the integrated circuit device according to the
modification.
[0155] In the integrated circuit device 8a according to the
modification as shown in FIG. 23, compared to the integrated
circuit device 8 according to the eighth embodiment described above
(referring to FIG. 17), the position of the stepped portion 21s of
the semiconductor member 21 is high. Specifically, in the eighth
embodiment described above, the two, i.e., upper and lower, levels
of the gate electrodes 25 oppose the upper portion 21u; but in the
modification, only the gate electrode 25a of the upper level and
the dummy electrode 25d of the upper level oppose the upper portion
21u; and the gate electrode 25b of the lower level and the dummy
electrode 25e of the lower level oppose the lower portion 211.
Also, the gate electrode 25b and the dummy electrode 25e of the
lower level are finer than the gate electrode 25a and the dummy
electrode 25d of the upper level.
[0156] According to the modification, the channel resistance of the
semiconductor member 21 can be reduced because the distance between
the gate electrode of the lower level and the channel of the gate
electrode of the upper level is shorter. On the other hand,
according to the eighth embodiment described above, because the
controllability by the gate electrode of the lower level is high
compared to the modification, the OFF current can be suppressed
effectively. Otherwise, the configuration, the manufacturing
method, and the effects of the modification are similar to those of
the eighth embodiment.
[0157] The modification may be combined with the eighth embodiment.
In other words, the semiconductor member 21 may have a three-level
configuration; the upper portion that opposes the gate electrode 25
of the upper level may be the finest; the central portion that
opposes the gate electrode 25 of the lower level may be the next
finer; and the lower portion that is connected to the local source
line 57 may be the widest. In such a case, stepped portions are
formed at the side surface of the semiconductor member 21 at two
locations separated in the Z-direction. The semiconductor member 21
may have a configuration of four levels or more. In such a case,
the stepped portions are formed at three or more locations.
Second Modification of Eighth Embodiment
[0158] A second modification of the eighth embodiment will now be
described.
[0159] FIG. 24 is a cross-sectional view showing the interconnect
selection unit of the integrated circuit device according to the
modification.
[0160] As shown in FIG. 24, the integrated circuit device 8b
according to the modification differs from the integrated circuit
device 8a according to the first modification (referring to FIG.
23) in that the stepped portion 21s of the semiconductor member 21
is formed only at a side surface facing one side in the X-direction
and is not formed at the side surface facing the other side.
Otherwise, the configuration, the manufacturing method, and the
effects of the modification are similar to those of the first
modification of the eighth embodiment.
Ninth Embodiment
[0161] A ninth embodiment will now be described.
[0162] FIG. 25 is a cross-sectional view showing the integrated
circuit device according to the embodiment.
[0163] As shown in FIG. 25, the integrated circuit device 9
according to the embodiment differs from the integrated circuit
device 5 according to the fifth embodiment described above
(referring to FIG. 13) in that the positions and lengths of the
gate electrodes 25 in the Z-direction are equal to each other; and
each of the electrodes 25 is formed of two types of materials
having mutually-different work functions.
[0164] Specifically, in the integrated circuit device 9, a gate
electrode 25s and a gate electrode 25t are arranged alternately
along the X-direction. The upper portion of the gate electrode 25s
is a standard work function portion 25N of which the work function
is a standard value; and the lower portion of the gate electrode
25s is a high work function portion 25H of which the value of the
work function is greater than the work function of the standard
work function portion 25N. The length of the standard work function
portion 25N is longer than the high work function portion 25H in
the Z-direction.
[0165] Also, the configuration of the gate electrode 25t is a
configuration in which the gate electrode 25s is vertically
inverted. In other words, the upper portion of the gate electrode
25t is the high work function portion 25H; and the lower portion of
the gate electrode 25t is the standard work function portion 25N.
In the gate electrode 25t as well, the length in the Z-direction of
the standard work function portion 25N is longer than the high work
function portion 25H. Therefore, as viewed from the X-direction,
the lower portion of the standard work function portion 25N of the
gate electrode 25s overlaps the upper portion of the standard work
function portion 25N of the gate electrode 25t. The same potential
is applied to the standard work function portion 25N and the high
work function portion 25H included in one gate electrode 25; and
the one gate electrode 25 can be treated as one electrode.
[0166] The combinations of the material of the standard work
function portion 25N (hereinbelow, also called the "standard
material") and the material of the high work function portion 25H
(hereinbelow, also called the "high work function material") are
arbitrary; it is sufficient to use a conductive material having
some of difference between the values of the work functions; and it
is favorable for the material to be handled easily in semiconductor
processes. For example, the standard material may be n-type
silicon; and the high work function material may be p-type silicon.
Also, two types of materials having mutually-different work
functions may be selected from metals or alloys. For example, the
standard material may be n-type silicon; and the high work function
material may be nickel (Ni), gold (Au), or tungsten (W), or nickel
silicide (NiSi.sub.x), palladium silicide (PdSi.sub.2), or platinum
silicide (PtSi.sub.2).
[0167] Operations of the integrated circuit device 9 according to
the embodiment will now be described.
[0168] If the work function of the gate electrode 25 is high, the
threshold voltage of the n-type transistor of that portion becomes
high; and the channel of that portion is easily switched to the OFF
state. On the other hand, if the work function of the gate
electrode 25 is low, the threshold voltage of the n-type transistor
of that portion becomes low; and the channel of that portion is
easily switched to the ON state.
[0169] Therefore, when the ON potential (e.g., 3 V) is applied to
one gate electrode 25s and one gate electrode 25t disposed on the
two sides of the selected member 21a and the OFF potential (e.g., 0
V) is applied to the other gate electrodes 25, the inversion layer
Ru is formed in the portion of the selected member 21a opposing the
standard work function portion 25N of the gate electrode 25s; the
inversion layer RI is formed in the portion of the selected member
21a opposing the standard work function portion 25N of the gate
electrode 25t; and a current flows in the selected member 21 by the
inversion layer Ru and the inversion layer RI being connected to
each other.
[0170] On the other hand, even in the case where the semiconductor
member 21 opposes the gate electrode 25 to which the ON potential
is applied, in the portion that opposes the high work function
portion 25H, an inversion layer is not formed; or the degree of the
formation of the inversion layer is weak. Also, in the portion of
the semiconductor member 21 opposing the gate electrode 25 to which
the OFF potential is applied, an inversion layer is not formed; or
the degree of the formation of the inversion layer is weak.
Therefore, in the half-selected members 21b and 21c disposed on the
two sides of the selected member 21a, the inversion layer is not
formed except in the upper portion or the lower portion of the
half-selected members 21b and 21c; or the degree of inversion is
weak. Therefore, in the half-selected members 21b and 21c, only a
current that is weaker than that of the selected member 21a flows;
or a current substantially does not flow.
[0171] Thus, in the integrated circuit device 9, while switching
the selected member 21a to the ON state, the current that flows in
the half-selected members 21b and 21c sharing the gate electrode 25
with the selected member 21a is reduced; and the half-selected
members 21b and 21c can approach the OFF state.
[0172] A method for manufacturing the integrated circuit device
according to the embodiment will now be described.
[0173] FIG. 26A to FIG. 28D are cross-sectional views showing the
method for manufacturing the integrated circuit device according to
the embodiment.
[0174] First, as shown in FIG. 26A, by patterning the upper layer
portion of the silicon substrate 12, the multiple local source
lines 57 are formed; and the semiconductor members 21 are multiply
formed on each of the local source lines 57 in columnar
configurations in which the n.sup.+-type portion 22, the
p.sup.--type portion 23, and the n.sup.+-type portion 24 are
stacked in this order. Then, for example, the silicon nitride film
62 are formed on the side surfaces of the semiconductor members 21
by ALD. Then, the insulating film 63a that includes silicon oxide
(e.g., SiO.sub.2) is filled by a PSZ method between the pillars
formed of the semiconductor members 21 and the silicon nitride
films 62.
[0175] Then, as shown in FIG. 26B, the upper portions of the
semiconductor members 21 and the upper portions of the silicon
nitride films 62 are caused to protrude from the upper surface of
the insulating film 63a by causing the upper surface of the
insulating film 63a to recede by performing etch-back of the
insulating film 63a.
[0176] Then, as shown in FIG. 26C, the upper portions of the
semiconductor members 21 are exposed by removing the exposed
portions of the silicon nitride films 62. Then, the thermal oxide
films 64 are formed on the surfaces of the upper portions of the
semiconductor members 21 by performing thermal oxidation
treatment.
[0177] Then, as shown in FIG. 26D, a p-type polysilicon film 67a is
deposited on the entire surface. Then, etch-back of the p-type
polysilicon film 67a is performed using the thermal oxide films 64
as a stopper.
[0178] Then, as shown in FIG. 27A, the mask film 66a is formed to
cover every other region of the regions between the semiconductor
members 21 arranged along the X-direction. Then, the upper surface
of the p-type polysilicon film 67a is caused to recede in every
other region of the regions between the semiconductor members 21 by
performing etching using the mask film 66a as a mask. Subsequently,
the mask film 66a is removed.
[0179] Then, as shown in FIG. 27B, the n-type polysilicon film 65a
is deposited on the entire surface. Then, etch-back of the n-type
polysilicon film 65a is performed using the thermal oxide films 64
as a stopper. Thereby, the n-type polysilicon film 65a is filled
into the space from which the p-type polysilicon film 67a was
removed in the process shown in FIG. 27A.
[0180] Then, as shown in FIG. 27C, the mask film 66b is formed in
the regions where the mask film 66a was not disposed in the process
shown in FIG. 27A; and the insulating film 63a is exposed by
removing the p-type polysilicon film 67a in the regions not covered
with the mask film 66b by performing etching using the mask film
66b as a mask.
[0181] Then, as shown in FIG. 27D, the n-type polysilicon film 65b
is deposited; and etch-back is performed using the mask film 66b as
a mask so that the n-type polysilicon film 65b remains in the
regions not covered with the mask film 66b. At this time, the upper
surface of the n-type polysilicon film 65b is set to be positioned
lower than the upper surface of the n-type polysilicon film
65a.
[0182] Then, as shown in FIG. 28A, a p-type polysilicon film 67b is
deposited. Then, etch-back of the p-type polysilicon film 67b is
performed using the thermal oxide films 64 as a stopper. Thereby,
in the process shown in FIG. 27D, the p-type polysilicon film 67b
is filled into the space from which the n-type polysilicon film 65b
was removed.
[0183] Then, as shown in FIG. 28B, the upper portions of the
semiconductor members 21 and the upper portions of the thermal
oxide films 64 are caused to protrude from the upper surfaces of
the n-type polysilicon film 65b and the p-type polysilicon film 67b
by causing the upper surfaces of the n-type polysilicon film 65b
and the p-type polysilicon film 67b to recede by performing
etch-back of the n-type polysilicon film 65b and the p-type
polysilicon film 67b.
[0184] Then, as shown in FIG. 28C, the insulating film 63b is
formed on the n-type polysilicon film 65b and the p-type
polysilicon film 67b by depositing an insulator by a PSZ method,
etc., and by performing etch-back using the thermal oxide films 64
as a stopper.
[0185] Then, as shown in FIG. 28D, the portions of the thermal
oxide films 64 disposed on the upper surfaces of the semiconductor
members 21 are removed. Thereby, the upper surfaces of the
semiconductor members 21 are exposed.
[0186] Thus, the gate electrode 25 that has one level extending in
the Y-direction is formed between the semiconductor members 21
arranged along the X-direction. In each of the gate electrodes 25,
the n-type polysilicon films 65a and 65b become the standard work
function portions 25N; and the p-type polysilicon films 67a and 67b
become the high work function portions 25H. Thereafter, the
integrated circuit device 9 is manufactured by normal methods.
[0187] Effects of the embodiment will now be described.
[0188] According to the embodiment, compared to the sixth
embodiment described above, operations similar to those of the
sixth embodiment can be realized by fewer gate electrodes 25. In
other words, because the portions of the standard work function
portions 25N overlap as viewed from the X-direction for the gate
electrodes 25s and 25t disposed on the two sides of the
semiconductor member 21, a large ON current can be caused to flow
in the selected semiconductor member 21. Also, because the current
in the portion of the semiconductor member 21 opposing the high
work function portion 25H can be blocked or weakened by the
existence of the high work function portion 25H, the OFF current of
the half-selected semiconductor members 21 can be reduced.
[0189] Also, in the embodiment, the standard work function portion
25N includes an n-type polysilicon film; and the high work function
portion 25H includes a p-type polysilicon film. Therefore, the
adhesion between the standard work function portion 25N and the
high work function portion 25H is good; and the formation of the
gate electrodes 25 by a silicon process is easy.
[0190] Otherwise, the configuration, the manufacturing method, the
operations, and the effects of the embodiment are similar to those
of the fifth embodiment described above.
Test Example
[0191] A test example having the effects of the first embodiment
described above will now be described.
[0192] FIG. 29A is an example of a graph showing the current
flowing in a selected semiconductor member (labeled "selected" in
the drawing) and the current flowing in a half-selected
semiconductor member (labeled "half-selected" in the drawing)
adjacent to the selected semiconductor member in the integrated
circuit device according to an example of the first embodiment
(referring to FIG. 1), where the horizontal axis is the drain
voltage, and the vertical axis is the drain current.
[0193] FIG. 29B is an example of a graph showing the current
flowing in the selected semiconductor member and the current
flowing in the half-selected semiconductor member of the integrated
circuit device according to the example of the first embodiment,
where the horizontal axis is the gate voltage, and the vertical
axis is the drain current.
[0194] FIG. 30A and FIG. 30B are examples of graphs of the electron
concentration inside the semiconductor member. FIG. 30A shows the
case where the ON potential is applied to the gate electrodes 25a
and 25b, the OFF potential is applied to the dummy electrodes 25d
and 25e, and the semiconductor member is switched to the ON state
(selected); and FIG. 30B shows the case where the ON potential is
applied to only the gate electrode 25b, the OFF potential is
applied to the gate electrode 25a and the dummy electrodes 25d and
25e, and the semiconductor member is switched to the OFF state
(half-selected).
[0195] The test example shown in FIG. 29A FIG. 29B, FIG. 30A, and
FIG. 30B was implemented by simulation. The "half-selected"
semiconductor member corresponds to the semiconductor members 21b
and 21c shown in FIG. 7. In other words, the "half-selected"
semiconductor member is the semiconductor member for which the ON
potential is applied to one of the gate electrodes disposed on the
two sides of the semiconductor member and the OFF potential is
applied to the other.
[0196] In the integrated circuit device according to the example of
the first embodiment as shown in FIGS. 30A and 30B, the current
flowing in the half-selected semiconductor member was about (
1/100) times the current flowing in the selected semiconductor
member; and a sufficiently high ON/OFF ratio could be realized. The
current flowing in the completely-unselected semiconductor members
for which the OFF potential was applied to both gate electrodes on
the two sides was about 1.times.10.sup.-13 [A/cell] and was
sufficiently low.
[0197] Also, in the integrated circuit device according to the
example of the first embodiment as shown in FIG. 30A and FIG. 30B,
the portion of the selected semiconductor member where the electron
concentration is not less than 1.times.10.sup.19 cm.sup.-3 existed
continuously along the Z-direction. On the other hand, the portion
of the half-selected semiconductor member where the electron
concentration is not less than 1.times.10.sup.18 cm.sup.-3 was
broken in the Z-direction and did not exist continuously along the
Z-direction.
[0198] According to the embodiments described above, an integrated
circuit device having good stability of operation can be
realized.
[0199] 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 novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments 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
invention. Additionally, the embodiments described above can be
combined mutually.
* * * * *