SEMICONDUCTOR MEMORY DEVICE AND METHOD FOR MANUFACTURING SAME
According to one embodiment, a semiconductor memory device includes a substrate, a semiconductor pillar provided on the substrate to extend in a vertical direction, a plurality of first electrode films provided sideward of the semiconductor pillar to extend in a first direction. The plurality of first electrode films are disposed to be separated from each other along the vertical direction. The semiconductor memory device further includes a plurality of second electrode films provided between the semiconductor pillar and the first electrode films. The plurality of second electrode films are disposed to be separated from each other along the vertical direction. The semiconductor memory device further includes a first insulating film provided between the semiconductor pillar and the second electrode films, and a second insulating film provided between the second electrode film and the first electrode film.
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This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2014-003793, filed on Jan. 10, 2014; the entire contents of which are incorporated herein by reference.
FIELDEmbodiments described herein relate generally to a semiconductor memory device and a method for manufacturing the same.
BACKGROUNDAlthough conventionally the planar structure of NAND flash memory has been shrunk to increase the bit density and reduce the bit cost, such shrink is approaching a limit. Therefore, in recent years, technology has been proposed to stack the memory cells in the vertical direction. The data retention characteristics of the memory cells are problematic in such a stacked memory device.
In general, according to one embodiment, a semiconductor memory device includes a substrate, a semiconductor pillar provided on the substrate to extend in a vertical direction, a plurality of first electrode films provided sideward of the semiconductor pillar to extend in a first direction. The plurality of first electrode films are disposed to be separated from each other along the vertical direction. The semiconductor memory device further includes a plurality of second electrode films provided between the semiconductor pillar and the first electrode films. The plurality of second electrode films are disposed to be separated from each other along the vertical direction. The semiconductor memory device further includes a first insulating film provided between the semiconductor pillar and the second electrode films, and a second insulating film provided between the second electrode film and the first electrode film.
First EmbodimentEmbodiments of the invention will now be described with reference to the drawings.
First, a first embodiment will be described.
As shown in
In the memory cell region Rm, an insulating film 11 (a third insulating film) that is made of, for example, silicon oxide, a conductive layer 12 that is made of, for example, polysilicon, an interconnect layer 13 that is made of, for example, tungsten, and a conductive layer 14 that is made of, for example, polysilicon are stacked in this order on the silicon substrate 10. A cell source line 15 is formed of the conductive layer 12, the interconnect layer 13, and the conductive layer 14. An insulating film 17 that is made of, for example, silicon oxide is provided on the cell source line 15. Multiple silicon pillars 20 that extend in the Z-direction are provided on the cell source line 15. The silicon pillars 20 are made of, for example, polysilicon; and the lower ends of the silicon pillars 20 pierce the insulating film 17 to be connected to the cell source line 15. The silicon pillars 20 are arranged in a matrix configuration along the X-direction and the Y-direction as viewed from the Z-direction and have a common connection with a single cell source line 15.
Multiple control gate electrode films (the first electrode films) 21 are provided sideward of the silicon pillar 20 to be separated from each other along the Z-direction. Each of the control gate electrode films 21 is made of, for example, tungsten and extends in the Y-direction. Therefore, the control gate electrode films 21 are not disposed between the silicon pillars 20 arranged along the Y-direction. Also, in the X-direction, two of the silicon pillars 20 are arranged alternately with two of the control gate electrode films 21. In other words, when the silicon pillars 20 arranged along the X-direction are organized into multiple sets 22 every two mutually-adjacent silicon pillars 20 and when two of the control gate electrode films 21 are arranged to be positioned between the sets 22, the control gate electrode films 21 are not disposed between the two silicon pillars 20 belonging to each set 22.
An inter-layer insulating film 23 is provided between the silicon pillars 20. An inter-layer insulating film 24 that is made of, for example, silicon oxide is provided between the control gate electrode films 21, below the control gate electrode film 21 of the lowermost layer, and above the control gate electrode film 21 of the uppermost layer. A hard mask 26 is provided on a stacked body 25 that is made of the multiple control gate electrode films 21, the inter-layer insulating film 23, and the inter-layer insulating film 24.
The silicon pillar 20 is drawn out onto the hard mask 26 to be a single body with an interconnect 27 extending in the X-direction. Thereby, the silicon pillars 20 that are arranged along the X-direction are connected to a common interconnect 27. A via 28 is provided on the interconnect 27; and a bit line 29 that extends in the X-direction is provided on the via 28. The bit line 29 is connected to the interconnect 27 by the via 28. Thus, each of the silicon pillars 20 is connected between the bit line 29 and the cell source line 15. In other words, the semiconductor memory device 1 is an I-shaped pillar type stacked memory device.
The Y-direction end portion of the stacked body 25 is patterned into a stairstep configuration; and at the end portion of the stairstep configuration, the multiple control gate electrode films 21 that have the same position in the Z-direction are bundled together. A via 38 is provided on the end portion of the bundled control gate electrode films 21. A word line 39 that extends in the Y-direction is provided on the via 38. In the Z-direction, the position of the word line 39 is the same as the position of the bit line 29. The word line 39 is connected to the control gate electrode film 21 by the via 38.
As shown in
A tunneling insulating film 33 that is made of, for example, silicon oxide is provided between the silicon pillar 20 and the floating gate electrode films 31. The tunneling insulating film 33 is provided at each silicon pillar 20; and the configuration of the tunneling insulating film 33 is a band configuration that extends in the Z-direction and has the X-direction as the thickness direction and the Y-direction as the width direction.
On the other hand, a blocking insulating film 34 is provided between the floating gate electrode film 31 and the control gate electrode film 21. The blocking insulating film 34 is, for example, a three-layer film in which a silicon nitride layer 35, a silicon oxide layer 36, and a silicon nitride layer 37 are stacked in this order from the floating gate electrode film 31 side toward the control gate electrode film 21 side. The silicon nitride layer 35 is formed around the floating gate electrode film 31 to cover an upper surface 31a and a lower surface 31b of the floating gate electrode film 31. The silicon oxide layer 36 and the silicon nitride layer 37 are formed around the control gate electrode film 21 to cover an upper surface 21a and a lower surface 21b of the control gate electrode film 21.
Although the tunneling insulating film 33 normally is insulative, the tunneling insulating film 33 is a film in which a tunneling current flows when a voltage within the range of the drive voltage of the semiconductor memory device 1 is applied. The blocking insulating film 34 is a film in which a current substantially does not flow even when a voltage within the range of the drive voltage of the semiconductor memory device 1 is applied. The equivalent oxide thickness (EOT) of the tunneling insulating film 33 is thicker than the equivalent oxide thickness of the blocking insulating film 34; and the dielectric constant of the tunneling insulating film 33 is lower than the dielectric constant of the blocking insulating film.
In the peripheral circuit region Rc as shown in
As described below, the insulating film 11 that is in the memory cell region Rm and the gate insulating film 41 that is in the peripheral circuit region Rc are formed by dividing the same silicon oxide film; the conductive layer 12 that is in the memory cell region Rm and the conductive layer 42 that is in the peripheral circuit region Rc are formed by dividing the same polysilicon layer; and the interconnect layer 13 that is in the memory cell region Rm and the interconnect layer 43 that is in the peripheral circuit region Rc are formed by dividing the same tungsten layer.
A method for manufacturing the semiconductor memory device according to the embodiment will now be described.
Only the memory cell region Rm is shown in
First, as shown in
Then, a polysilicon layer is formed on the entire surface. STI (Shallow Trench Isolation) is formed in the upper layer portion of the silicon substrate 10 in the peripheral circuit region Rc using an appropriate mask (not shown). Then, a tungsten layer is formed. Then, a polysilicon layer and a silicon oxide film are formed only in the memory cell region Rm. Then, these layers are patterned by RIE (Reactive Ion Etching).
Thereby, the insulating film 11, the conductive layer 12, the interconnect layer 13, the conductive layer 14, and the insulating film 17 are formed for each block in the memory cell region Rm. The cell source line 15 is formed of the stacked body made of the conductive layer 12, the interconnect layer 13, and the conductive layer 14. Erasing is possible by block unit by forming the cell source line 15 to be divided for each block. On the other hand, the gate insulating film 41, the conductive layer 42, and the interconnect layer 43 are formed in the peripheral circuit region Rc. The gate electrode 45 is formed of the stacked body made of the conductive layer 42 and the interconnect layer 43. Thereby, the transistor 46 is formed in the peripheral circuit region Rc.
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Effects of the embodiment will now be described.
In the embodiment, the floating gate electrode films 31 that are made of polysilicon are provided as charge storage units. Therefore, the data retention characteristics of the memory cells are good; and the erasing operation is fast because the charge that is stored in the floating gate electrode films 31 can be erased by moving electrons instead of holes. The data retention characteristics are even better because the floating gate electrode films 31 are separated from each other.
In the embodiment, because the blocking insulating film 34 is a three-layer film made of the silicon nitride layer 35, the silicon oxide layer 36, and the silicon nitride layer 37, the coupling ratio can be ensured while suppressing the leakage current. Also, the silicon nitride layer 35 is formed from the silicon pillar 20 side in the process shown in
Thus, by dividing the three-layer film of the blocking insulating film 34 into two and forming the three-layer film from both sides, compared to the case of forming from only one side, the thickness of the blocking insulating film 34 can be distributed on the two X-direction sides of the floating gate electrode film 31; and the thickness in the Z-direction as an entirety can be reduced. Thereby, the height in the Z-direction of the recesses 54 (referring to
In the embodiment, the blocking insulating film 34 is divided for each of the control gate electrode films 21 along the Z-direction. Thereby, the electrons that are stored in the floating gate electrode film 31 can be prevented from propagating through the blocking insulating film 34 and leaking. As a result, the data retention characteristics of the memory cells are good.
In the embodiment, as shown in
Although an example is illustrated in the embodiment in which the blocking insulating film 34 is a three-layer film, this is not limited thereto. The layers of the blocking insulating film 34 are not limited to the silicon oxide layer (the SiO2 layer) and the silicon nitride layers (the Si3N4 layers) and may be a high dielectric constant layer such as, for example, an Al2O3 layer, a MgO layer, a SrO layer, a SiN layer, a BaO layer, a TiO layer, a Ta2O5 layer, a BaTiO3 layer, a BaZrO layer, a ZrO2 layer, a Y2O3 layer, a ZrSiO layer, a HfAlO layer, a HfSiO layer, a La2O3 layer, a LaAlO layer, etc.
Although an example is illustrated in the embodiment in which the floating gate electrode film 31 is formed of polysilicon, the floating gate electrode film 31 is not limited thereto and may be formed of, for example, a metal silicide or a metal.
Although an example is illustrated in the embodiment in which the control gate electrode film 21 is formed of tungsten, the control gate electrode film 21 is not limited thereto and may be formed of, for example, a metal silicide by filling a polysilicon film and subsequently siliciding the polysilicon film.
In the process shown in
Several layers of the control gate electrode films 21 provided at the upper portion of the stacked body 25 may be shorted to each other to be used as the selection gate electrode film; and several layers of the control gate electrode films 21 provided at the lower portion of the stacked body 25 may be shorted to each other to be used as the selection gate electrode film. Thereby, a selection transistor that has a gate length longer than that of the memory cell transistor can be formed.
Modification of First EmbodimentA modification of the embodiment will now be described.
In the semiconductor memory device is according to the modification as shown in
In the semiconductor memory device is according to the modification, the two X-direction side portions of the wide silicon pillar 65 are used as distinct channels. Otherwise, the configuration, the manufacturing method, and the effects of the modification are similar to those of the first embodiment described above.
Second EmbodimentA second embodiment will now be described.
As shown in
In other words, in the semiconductor memory device 2, the blocking insulating film 34 is disposed between the silicon pillar 20 and the floating gate electrode films 31; and the tunneling insulating film 33 is disposed between the floating gate electrode films 31 and the control gate electrode films 21.
Therefore, the components included in the memory cell are arranged in the order of silicon pillar 20-blocking insulating film 34-floating gate electrode film 31-tunneling insulating film 33-control gate electrode film 21.
More specifically, in the semiconductor memory device 2, silicon oxide films 71 are arranged to be separated from each other along the Z-direction; and the floating gate electrode films 31 and the control gate electrode films 21 are provided in the spaces between the mutually-adjacent silicon oxide films 71. Also, the tunneling insulating film 33 is disposed to cover the upper surface and the lower surface of the control gate electrode film 21 and the side surface of the control gate electrode film 21 on the floating gate electrode film 31 side. On the other hand, the blocking insulating film 34 is disposed linearly along the side surface of the silicon pillar 20.
Similarly to the first embodiment, the blocking insulating film 34 may be a multilayered film, e.g., a three-layer film. However, the blocking insulating film 34 is not subdivided between the silicon pillar 20 side and the control gate electrode film 21 side; and the entire blocking insulating film 34 is disposed on the silicon pillar 20 side.
In the semiconductor memory device 2, the lower end portions of the two silicon pillars 20 belonging to the set 22 are connected to each other; and the cell source line 15 is not provided. A source line (not shown) is provided above the stacked body. In other words, the semiconductor memory device 2 is a U-shaped pillar type stacked memory device. Otherwise, the configuration of the embodiment is similar to that of the first embodiment described above.
The basic operations and the read-out method of the semiconductor memory device 2 are similar to those of a normal NAND flash memory; and the polarity of the voltage applied between the silicon pillar 20 and the control gate electrode film 21 in the programming operation and the erasing operation are the reverse of those of a normal NAND flash memory. Thereby, the charge is caused to move into and out of the silicon pillar 20 from the control gate electrode film 21.
A method for manufacturing the semiconductor memory device according to the embodiment will now be described.
First, as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Effects of the embodiment will now be described.
In the programming operation and the erasing operation of a NAND memory device, it is necessary for the current to flow in the tunneling insulating film and for the current to not flow easily in the blocking insulating film. To this end, it is necessary for the physical film thickness of the blocking insulating film to be thicker than the physical film thickness of the tunneling insulating film. Accordingly, if the blocking insulating film 34 is to be formed to extend around into the gaps between the silicon oxide films 71, it is necessary to set the spacing between the silicon oxide films 71 to be long in the Z-direction, which obstructs higher integration of the memory cells in the Z-direction. Further, the aspect ratio of the trenches 75 and 78 undesirably increases; and patterning becomes difficult.
If the spacing of the silicon oxide films 71 nevertheless is set to be short, the thickness of the control gate electrode film 21, which is covered with the blocking insulating film 34 at the upper surface and the lower surface of the control gate electrode film 21, becomes shorter than the spacing of the silicon oxide films 71. Accordingly, the interconnect resistance of the control gate electrode film 21 increases; the gate length of the memory cell transistor becomes short; and the characteristics of the memory cell transistor undesirably degrade due to the short channel effect.
Conversely, in the embodiment, the blocking insulating film 34 is formed on the inner surface of the trench 75 in the process shown in
A first modification of the embodiment will now be described.
A second modification of the embodiment will now be described.
In the semiconductor memory device 2b according to the modification as shown in
To connect the lower end of the silicon pillar 20 to the cell source line 15 when manufacturing the semiconductor memory device 2b according to the modification, it is necessary for the portion of the blocking insulating film 34 formed on the bottom surface of the trench 75 to be removed by etching in the process shown in
A third modification of the embodiment will now be described.
As shown in
A third embodiment will now be described.
Compared to the semiconductor memory device 2 (referring to
A method for manufacturing the semiconductor memory device according to the embodiment will now be described.
First, as shown in
Then, the processes shown in
Thereby, as shown in
Then, as shown in
According to the embodiment, because the air gap 86 is made between the silicon pillars 20, the control gate electrode films 21, the floating gate electrode films 31, the tunneling insulating films 33, and the blocking insulating films 34, the proximity effect can be suppressed; and the breakdown voltage can be increased.
Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the second embodiment described above.
It is possible for the air gap to be made only between the silicon pillars 20 by alternately stacking the silicon oxide film 71 and the polysilicon film 72 instead of the silicon nitride film 87 and the polysilicon film 72 in the process shown in
A modification of the embodiment will now be described.
As shown in
In the modification as shown in
According to the modification, by providing the reinforcing member 89, the mechanical strength of the semiconductor memory device 3a can be ensured; and collapse can be prevented. Otherwise, the configuration, the manufacturing method, the operations, and the effects of the modification are similar to those of the third embodiment described above.
Fourth EmbodimentA fourth embodiment will now be described.
As shown in
The semiconductor memory device according to the embodiment will now be described.
First, the processes shown in
Then, as shown in
Continuing as shown in
According to the embodiment, the control gate electrode film 21u of the uppermost level and the floating gate electrode film 31u of the uppermost level can be electrically integrated to be used as the selection gate electrode film by causing the control gate electrode film 21u to connect the floating gate electrode film 31u. Thereby, a selection gate transistor can be formed in which the threshold does not fluctuate because charge is not stored.
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 EmbodimentA fifth embodiment will now be described.
In the semiconductor memory device 5 according to the embodiment as shown in
The tunneling insulating films 33 and the floating gate electrode films 31 are divided in the Z-direction. The silicon oxide films 51 are provided between the stacked bodies having the circular ring configurations made of the tunneling insulating film 33 and the floating gate electrode film 31 in the Z-direction. In the floating gate electrode film 31, a polysilicon layer 91 is disposed on the inner side; and a metal silicide layer 92 is disposed on the outer side. The metal silicide layer 92 is formed of a metal silicide but may be formed of a metal.
In the blocking insulating film 34, a silicon oxide layer 93 is disposed on the inner side; and high dielectric constant layers 94 are disposed on the outer side. The high dielectric constant layers 94 are made of a material having a higher dielectric constant than silicon oxide, for example, hafnium (Hf), aluminum oxide (AlO), titanium nitride (TiN), tantalum nitride (TaN), or tantalum oxide (TaO). The silicon oxide layer 93 is provided continuously in a tubular configuration in the Z-direction. However, the diameter of the tube fluctuates periodically such that the diameter of the portions corresponding to the floating gate electrode films 31 is relatively small and the diameter of the portions corresponding to the silicon oxide films 51 is relatively large. Therefore, the silicon oxide layer 93 has a circular tubular bellows-like configuration. The high dielectric constant layers 94 are disposed inside recesses 93a at the outer surface of the circular tubular bellows-like configuration made of the silicon oxide layer and are divided for each of the recesses 93a. The configuration of the blocking insulating film 34 is not limited to the two-layer structure made of the silicon oxide layer 93 and the high dielectric constant layers 94. For example, the configuration may be a combination of any layer of a silicon oxide layer (a SiO2 layer), a silicon nitride layer (a Si3N4 layer), an Al2O3 layer, a MgO layer, a SrO layer, a SiN layer, a BaO layer, a TiO layer, a Ta2O5 layer, a BaTiO3 layer, a BaZrO layer, a ZrO2 layer, a Y2O3 layer, a ZrSiO layer, a HfAlO layer, a HfSiO layer, a La2O3 layer, a LaAlO layer, etc.
In the semiconductor memory device 5, the multiple control gate electrode films 21 are provided to be arranged in a matrix configuration along the X-direction and the Z-direction. The control gate electrode films 21 have band configurations extending in the Y-direction. The control gate electrode film 21 is a conductive film, e.g., a two-layer film made of a titanium nitride layer (TiN) and a tungsten layer (W), a two-layer film made of a tungsten nitride layer (WN) and a tungsten layer (W), or a two-layer film made of a tantalum nitride layer (TaN) and a tungsten layer (W). However, the configuration of the control gate electrode film 21 is not limited thereto; and, for example, a metal silicide layer formed by siliciding a polysilicon film may be used.
The structural body that is made of the silicon pillar 20, the tunneling insulating film 33, the floating gate electrode films 31, and the blocking insulating film 34 pierces the control gate electrode films 21. The control gate electrode films 21 are disposed in the recesses 93a. In other words, the control gate electrode films 21 are provided around the floating gate electrode films 31 as viewed from the Z-direction. The inter-layer insulating film 24 is provided between the structural bodies made of the silicon pillar 20, the tunneling insulating film 33, the floating gate electrode films 31, the blocking insulating film 34, and the control gate electrode films 21.
A method for manufacturing the semiconductor memory device according to the embodiment will now be described.
First, similarly to the first embodiment described above, the insulating film 11, the cell source line 15, and the insulating film 17 (referring to
Then, as shown in
Continuing, multiple memory holes 95 are made in the stacked body 60. The memory holes 95 extend in the Z-direction and pierce the stacked body 60 and the insulating film 17 (referring to
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Effects of the embodiment will now be described.
According to the embodiment, memory cells having good controllability can be realized because the control gate electrode films 21 are provided around the floating gate electrode films 31 and the silicon pillar 20.
The programming characteristics are good because the floating gate electrode films 31 are formed of conductors. Also, because the floating gate electrode films 31 are separated from each other, the movement of the charge is suppressed; and the data retention characteristics are high. The erasing characteristics are good because the erasing operations can be implemented by FN erasing or assisted erasing from the floating gate electrode films 31.
In the embodiment, it is unnecessary to remove the tunneling insulating film 33 formed on the bottom surface of the memory hole 95 by etching because the silicon pillar 20 is connected to the cell source line 15 (referring to
Otherwise, the configuration, the manufacturing method, the operations, and the effects of the embodiment are similar to those of the first embodiment described above. Although an I-shaped pillar type device is illustrated in the embodiment, a U-shaped pillar type device may be used similarly to the first modification of the second embodiment described above.
Modification of Fifth EmbodimentA modification of the fifth embodiment will now be described.
As shown in
A method for manufacturing the semiconductor memory device according to the modification will now be described.
First, the processes shown in
Then, as shown in
Continuing as shown in
Then, as shown in
Continuing, the process shown in
According to the modification, similarly to the fourth embodiment described above, the control gate electrode film 21u and the floating gate electrode film 31u of the uppermost level can be electrically integrated to be used as the selection gate electrode film. As a result, a selection gate transistor can be formed in which the threshold does not fluctuate. Otherwise, the configuration, the manufacturing method, the operations, and the effects of the modification are similar to those of the fifth embodiment described above.
According to the embodiments described above, a semiconductor memory device having good data retention characteristics and a method for manufacturing the semiconductor memory device can be realized.
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.
Claims
1. A semiconductor memory device, comprising:
- a substrate;
- a semiconductor pillar provided on the substrate to extend in a vertical direction;
- a plurality of first electrode films provided sideward of the semiconductor pillar to extend in a first direction, the plurality of first electrode films being disposed to be separated from each other along the vertical direction;
- a plurality of second electrode films provided between the semiconductor pillar and the first electrode films, the plurality of second electrode films being disposed to be separated from each other along the vertical direction;
- a first insulating film provided between the semiconductor pillar and the second electrode films; and
- a second insulating film provided between the second electrode film and the first electrode film.
2. The device according to claim 1, wherein
- an equivalent oxide thickness of the first insulating film is thicker than an equivalent oxide thickness of the second insulating film, and
- a dielectric constant of the first insulating film is lower than a dielectric constant of the second insulating film.
3. The device according to claim 2, wherein the second insulating film includes:
- a first layer provided on the first electrode film side to cover an upper surface and a lower surface of the first electrode film; and
- a second layer provided on the second electrode film side to cover an upper surface and a lower surface of the second electrode film.
4. The device according to claim 1, wherein
- an equivalent oxide thickness of the second insulating film is thicker than an equivalent oxide thickness of the first insulating film, and
- a dielectric constant of the second insulating film is lower than a dielectric constant of the first insulating film.
5. The device according to claim 4, wherein the first insulating film is disposed along a side surface of the semiconductor pillar.
6. The device according to claim 1, wherein
- a plurality of the semiconductor pillars are provided,
- the plurality of semiconductor pillars is arranged in a matrix configuration along the first direction and a second direction intersecting the first direction as viewed from above,
- the first electrode film is not disposed between the semiconductor pillars arranged along the first direction, and
- when the semiconductor pillars arranged along the second direction are organized into sets every two mutually-adjacent semiconductor pillars and when two of the first electrode films are positioned between the sets, the first electrode films are not disposed between the two semiconductor pillars belonging to each set.
7. The device according to claim 6, wherein the two semiconductor pillars belonging to the set are formed as one body.
8. The device according to claim 6, wherein a length in the first direction of an end portion of the second electrode film on the semiconductor pillar side is shorter than a length in the first direction of an end portion of the second electrode film on the first electrode film side.
9. The device according to claim 6, wherein an air gap is made in at least one location between the semiconductor pillars, between the first electrode films adjacent to each other in the vertical direction, and/or between the second electrode films adjacent to each other in the vertical direction.
10. The device according to claim 1, wherein the second electrode films are provided around the semiconductor pillar as viewed from above, and the first electrode films are provided around the second electrode films as viewed from above.
11. The device according to claim 1, wherein the second insulating film is not disposed between the first electrode film and the second electrode film for the uppermost level or for a plurality of levels including the uppermost level, and the first electrode film is connected to the second electrode film for the uppermost level or for the plurality of levels including the uppermost level.
12. The device according to claim 1, wherein the second insulating film is divided along the vertical direction for each of the first electrode films.
13. The device according to claim 1, further comprising:
- a cell source line provided between the substrate and the semiconductor pillar to be connected to a lower end of the semiconductor pillar;
- a bit line provided on the semiconductor pillar to be connected to an upper end of the semiconductor pillar;
- a third insulating film provided between the substrate and the cell source line;
- a source region and a drain region formed to be separated from each other in a region of the substrate distal to a region directly under the semiconductor pillar;
- a fourth insulating film provided in a region directly above a region of the substrate between the source region and the drain region; and
- a gate electrode provided on the fourth insulating film.
14. A method for manufacturing a semiconductor memory device, comprising:
- forming a stacked body on a substrate by alternately stacking an insulating film and a first film;
- making a first trench in the stacked body to extend in a first direction;
- making a first recess by causing an exposed surface of the first film at an inner surface of the first trench to recede;
- forming a first insulating layer on the inner surface of the first trench;
- forming a first conductive film on the first insulating layer;
- removing a part of the first conductive film and a part of the first insulating layer located outside the first recess by etching and remaining another part of the first conductive film and another part of the first insulating layer located inside the first recess;
- forming a first insulating film on the inner surface of the first trench;
- forming a semiconductor film on the first insulating film;
- making a second trench in the stacked body between the first trenches to extend in the first direction;
- making a second recess by removing the first film via the second trench;
- forming a second insulating layer on an inner surface of the second recess;
- forming a second conductive film inside the second recess; and
- dividing the semiconductor film and the first conductive film along the first direction,
- an equivalent oxide thickness of a second insulating film made of the first insulating layer and the second insulating layer being thinner than an equivalent oxide thickness of the first insulating film, a dielectric constant of the second insulating film being higher than a dielectric constant of the first insulating film.
15. The method according to claim 14, further comprising filling an inter-layer insulating film into the first trench after the forming of the semiconductor film and prior to the making of the second trench,
- the making of the first trench including: forming a first mask on the stacked body in a line-and-space configuration extending in the first direction; and performing anisotropic etching using the first mask,
- the dividing of the semiconductor film and the first conductive film along the first direction including: forming a second mask on the first mask in a line-and-space configuration extending in a second direction intersecting the first direction; making a through-hole by selectively removing the inter-layer insulating film and the semiconductor film by performing anisotropic etching using the second mask and the first mask; and performing isotropic etching of the first conductive film via the through-hole.
16. The method according to claim 14, further comprising forming a second film on a back surface of the first recess after the making of the first recess and prior to the forming of the first insulating layer, the second film being made of a material different from a material of the first film,
- the making of the second recess including removing the first film using the second film as a stopper.
17. A method for manufacturing a semiconductor memory device, comprising:
- forming a stacked body on a substrate by alternately stacking an insulating film and a first conductive film;
- making a first trench in the stacked body to extend in a first direction;
- forming a first insulating film on an inner surface of the first trench;
- forming a semiconductor film on the first insulating film;
- making a second trench in the stacked body between the first trenches to extend in the first direction;
- making a recess by causing an exposed surface of the first conductive film at an inner surface of the second trench to recede;
- forming a second insulating film on an inner surface of the recess, an equivalent oxide thickness of the second insulating film being thicker than an equivalent oxide thickness of the first insulating film, a dielectric constant of the second insulating film being lower than a dielectric constant of the first insulating film;
- forming a second conductive film inside the recess; and
- dividing the semiconductor film and the first conductive film along the first direction.
Type: Application
Filed: Mar 11, 2014
Publication Date: Jul 16, 2015
Applicant: Kabushiki Kaisha Toshiba (Minato-ku)
Inventors: Wataru SAKAMOTO (Mie-ken), Ryota Suzuki (Mie-ken), Tatsuya Okamoto (Mie-ken), Tatsuya Kato (Mie-ken)
Application Number: 14/204,623