Method for manufacturing nonvolatile semiconductor memory device and nonvolatile semiconductor memory device

1. A method for manufacturing a nonvolatile semiconductor memory device, the device including a stacked structural unit including a plurality of insulating films alternately stacked with a plurality of electrode films in a first direction and a semiconductor pillar piercing the stacked structural unit in the first direction, the method comprising:

forming a stacked unit including a core material film alternately stacked with a sacrificial film on a major surface of a substrate perpendicular to the first direction;

making a trench in the stacked unit, the trench extending in the first direction and a second direction in a plane perpendicular to the first direction;

filling a filling material into the trench;

removing the sacrificial film to form a hollow structural unit, the hollow structural unit including a post unit supporting the core material film on the substrate, the post unit being made of the filling material; and

forming the stacked structural unit by stacking one of the insulating films and one of the electrode films on a surface of the core material film exposed by removing the sacrificial film,

wherein spacing between the core material films increases as a distance from the post unit increases.

2. The method according to claim 1 , wherein a second thickness of a second portion of the core material film is thinner than a first thickness of a first portion of the core material film, the first portion being proximal to the post unit, the second portion being more distal than the first portion to the post unit.

3. The method according to claim 1 , wherein an etching rate of the core material film in the removing the sacrificial film and an etching rate of the sacrificial film in the removing the sacrificial film are mutually different.

4. The method according to claim 1 , wherein a film formation rate of the sacrificial film is higher than a film formation rate of the core material film.

5. The method according to claim 1 , wherein the sacrificial film includes amorphous silicon and the core material film includes a silicon oxide film.

6. The method according to claim 5 , wherein the filling material includes a silicon oxide film.

7. The method according to claim 6 , wherein the electrode film includes amorphous silicon and the insulating film includes a silicon oxide film.

8. The method according to claim 1 , wherein the sacrificial film includes a silicon oxide film and the core material film includes amorphous silicon.

9. A method for manufacturing a nonvolatile semiconductor memory device, the device including a stacked structural unit including a plurality of insulating films alternately stacked with a plurality of electrode films in a first direction and a semiconductor pillar piercing the stacked structural unit in the first direction, the method comprising:

forming a stacked unit including a core material film alternately stacked with a sacrificial film on a major surface of a substrate perpendicular to the first direction;

making a trench in the stacked unit, the trench extending in the first direction and a second direction in a plane perpendicular to the first direction;

filling a filling material into the trench;

removing the sacrificial film to form a hollow structural unit, the hollow structural unit including a post unit supporting the core material film on the substrate, the post unit being made of the filling material; and

forming the stacked structural unit by stacking one of the insulating films and one of the electrode films on a surface of the core material film exposed by removing the sacrificial film,

wherein the making the trench includes making a hole in the stacked unit simultaneously with the making the trench, the hole becoming an opening configured to allow an etchant to enter into an interior of the stacked unit to remove the sacrificial film, a width of the hole being wider than a width of the trench as viewed from the first direction.

10. The method according to claim 9 , wherein the removing the sacrificial film is performed from a side proximal to the opening of the sacrificial film.

11. The method according to claim 9 , wherein the filling material leaves a gap in the hole while being filled into the trench.

12. The method according to claim 9 , wherein the trench is multiply provided, the hole is provided between the plurality of trenches, and the hole is surrounded by the plurality of trenches.

13. The method according to claim 9 , wherein:

the trench is multiply provided to extend in a second direction orthogonal to the first direction, ends of each of the plurality of trenches being linked to each other;

the hole is provided between each of the plurality of trenches, the hole extending in the second direction; and

a width of the trench along a third direction orthogonal to the first direction and the second direction is shorter than a width of the hole along the third direction.

14. The method according to claim 9 , wherein the making the trench includes:

multiply making the trench to extend in a second direction orthogonal to the first direction;

making the hole between each of the plurality of trenches to extend in the second direction; and

making a first traversing hole and a second traversing hole to extend in a third direction orthogonal to the first direction and the second direction to link ends of each of the plurality of trenches, a width of the first traversing hole and a width of the second traversing hole along the second direction being shorter than a width of the hole along the third direction.

15. The method according to claim 14 , wherein the hole is surrounded by the plurality of trenches, the first traversing hole, and the second traversing hole.

16. The method according to claim 9 , wherein the hole is provided in a discrete configuration upon the stacked structural unit being viewed along the first direction.

17. The method according to claim 16 , wherein the making the trench includes making a narrow hole in the stacked structural unit, the narrow hole being provided between the holes provided in a discrete configuration to link the holes provided in a discrete configuration, and a width of the narrow hole being narrower than a width of the holes.

18. The method according to claim 9 , wherein the core material film forms a portion of the insulating film.