Semiconductor memory device and method of manufacturing the same

1. A semiconductor memory device, comprising:

a semiconductor substrate;

a transistor disposed on the semiconductor substrate;

a memory cell array disposed above the transistor, the memory cell array including a plurality of first conductive layers stacked in a first direction, a pillar extending through the plurality of first conductive layers in the first direction and containing a semiconductor layer, and a second conductive layer disposed below a bottommost layer of the plurality of first conductive layers and being in contact with the semiconductor layer, the memory cell array electrically connected to the transistor;

a first nitride layer disposed in a position between the transistor and the memory cell array in the first direction;

a second nitride layer disposed in a position between the transistor and the first nitride layer in the first direction; and

a conductor extending through the second nitride layer, the first nitride layer, and the plurality of first conductive layers in the first direction, wherein

a content of hydrogen in the second nitride layer is different from a content of hydrogen in the first nitride layer.

2. The device according to claim 1 , wherein

the content of hydrogen in the second nitride layer is lower than the content of hydrogen in the first nitride layer.

3. The device according to claim 1 , wherein

a density of the second nitride layer is lower than a density of the first nitride layer.

4. The device according to claim 1 , wherein

an etching rate of the second nitride layer is greater than an etching rate of the first nitride layer.

5. The device according to claim 1 , wherein

the transistor is a MOS transistor, and the MOS transistor includes boron-containing polycrystalline silicon.

6. The device according to claim 1 , wherein

the first nitride layer and the second nitride layer have respective cross sections cut along planes intersecting the first direction, wherein the respective cross sections both have areas which are greater than an area of a cross section of each of the first conducive layers cut along a plane intersecting the first direction.

7. The device according to claim 1 , wherein

the device is a NAND flash memory.

8. A semiconductor memory device, comprising:

a semiconductor substrate;

a transistor disposed on the semiconductor substrate;

a memory cell array disposed above the transistor, the memory cell array including a plurality of first conductive layers stacked in a first direction, a pillar extending through the plurality of first conductive layers in the first direction and containing a semiconductor layer, and a second conductive layer disposed below a bottommost layer of the plurality of first conductive layers and being in contact with the semiconductor layer, the memory cell array electrically connected to the transistor;

a first nitride layer disposed in a position between the transistor and the memory cell array in the first direction;

a second nitride layer disposed in a position between the transistor and the first nitride layer in the first direction; and

a conductor extending through the second nitride layer, the first nitride layer, and the plurality of first conductive layers in the first direction, wherein

a density of the second nitride layer is different from a density of the first nitride layer.

9. The device according to claim 8 , wherein

the density of the second nitride layer is lower than the density of the first nitride layer.

10. The device according to claim 8 , wherein

the transistor is a MOS transistor, and the MOS transistor includes boron-containing polycrystalline silicon.

11. The device according to claim 8 , wherein

the first nitride layer and the second nitride layer have respective cross sections cut along planes intersecting the first direction, wherein the respective cross sections both have areas which are greater than an area of a cross section of each of the first conductive layers cut along a plane intersecting the first direction.

12. The device according to claim 8 , wherein

the device is a NAND flash memory.

13. A semiconductor memory device, comprising:

a semiconductor substrate;

a transistor disposed on the semiconductor substrate;

a memory cell array disposed above the transistor, the memory cell array including a plurality of first conductive layers stacked in a first direction, a pillar extending through the plurality of first conductive layers in the first direction and containing a semiconductor layer, and a second conductive layer disposed below a bottommost layer of the plurality of first conductive layers and being in contact with the semiconductor layer, the memory cell array electrically connected to the transistor;

a first nitride layer disposed in a position between the transistor and the memory cell array in the first direction;

a second nitride layer disposed in a position between the transistor and the first nitride layer in the first direction; and

a conductor extending through the second nitride layer, the first nitride layer, and the plurality of first conductive layers in the first direction, wherein

an etching rate of the second nitride layer is different from an etching rate of the first nitride layer.

14. The device according to claim 13 , wherein

the etching rate of the second nitride layer is greater than the etching rate of the first nitride layer.

15. The device according to claim 13 , wherein

the transistor is a MOS transistor, and the MOS transistor includes boron-containing polycrystalline silicon.

16. The device according to claim 13 , wherein

the first nitride layer and the second nitride layer have respective cross sections cut along planes intersecting the first direction, wherein the respective cross sections both have areas which are greater than an area of a cross section of each of the first conductive layers cut along a plane intersecting the first direction.

17. The device according to claim 13 , wherein

the device is a NAND flash memory.