Nonvolatile storage device and method for manufacturing the same in which insulating film is located between first and second impurity diffusion regions but absent on first impurity diffusion region

1. A nonvolatile storage device, comprising:

a semiconductor substrate;

a gate electrode provided on the semiconductor substrate;

a first impurity diffusion region and a second impurity diffusion region which are provided in the semiconductor substrate on opposite sides sandwiching the gate electrode; and

a film stack extending from between the semiconductor substrate and the gate electrode onto at least a surface of the gate electrode lying on a first impurity diffusion region side and being in contact with the first impurity diffusion region, the film stack including a charge accumulating layer and a tunnel insulating film sequentially from a gate electrode side,

wherein an insulating film A is located in at least a part of a portion of the film stack and further wherein the insulating film A is located between the first impurity diffusion region and the second impurity diffusion region but absent on the first impurity diffusion region, and has a lower charge trap surface density than a portion of the charge accumulating layer located on the first impurity diffusion region.

2. The nonvolatile storage device according to claim 1 ,

wherein the charge trap surface density of the insulating film A is 0.

3. The nonvolatile storage device according to claim 1 ,

wherein the film stack is formed so as to extend from between the semiconductor substrate and the gate electrode onto only the surface of the gate electrode lying on the first impurity diffusion region side, and

the first impurity diffusion region is deeper than the second impurity diffusion region in a thickness direction of the semiconductor substrate.

4. The nonvolatile storage device according to claim 1 ,

wherein the insulating film A is formed so as to be absent on the second impurity diffusion region, and

the film stack is formed so as to further extend from between the semiconductor substrate and the gate electrode onto a surface of the gate electrode lying on a second impurity diffusion region side.

5. A nonvolatile storage device, comprising:

a semiconductor substrate;

a plurality of line electrodes extending in a predetermined direction on the semiconductor substrate so as to be parallel with each other;

a plurality of pairs of first and second impurity diffusion regions provided in the semiconductor substrate so as to sandwich each of the line electrodes therebetween in a direction perpendicular to the predetermined direction;

gate electrodes comprising portions of the line electrodes sandwiched between the first impurity diffusion regions and the second impurity diffusion regions; and

film stacks extending from between the semiconductor substrate and the gate electrodes onto at least surfaces of the gate electrodes lying on a first impurity diffusion region side and being in contact with the first impurity diffusion regions, the film stacks including charge accumulating layers and tunnel insulating films sequentially from a gate electrode side.

6. The nonvolatile storage device according to claim 5 ,

wherein the surfaces of the gate electrodes lying on the first impurity diffusion region side provided with the film stacks thereon extend vertically to the semiconductor substrate.

7. The nonvolatile storage device according to claim 5 ,

wherein insulating films A are located in at least a part of portions of the film stacks and further wherein the insulating films A are located between the first impurity diffusion regions and the second impurity diffusion regions but absent on the first impurity diffusion regions, and have a lower charge trap surface density than portions of the charge accumulating layers located on the first impurity diffusion regions.

8. The nonvolatile storage device according to claim 7 ,

wherein the charge trap surface density of the insulating films A is 0.

9. The nonvolatile storage device according to claim 7 ,

wherein the insulating films A are formed so as to be absent on the second impurity diffusion region, and

the film stacks are formed so as to further extend from between the semiconductor substrate and the gate electrodes onto surfaces of the gate electrodes lying on a second impurity diffusion region side.

10. The nonvolatile storage device according to claim 5 ,

wherein the film stacks are formed so as to extend from between the semiconductor substrate and the gate electrodes onto only the surfaces of the gate electrodes lying on the first impurity diffusion region side, and

the first impurity diffusion regions are deeper than the second impurity diffusion regions in a thickness direction of the semiconductor substrate.

11. The nonvolatile storage device according to claim 5 ,

wherein the film stacks are formed so as to further extend from between the semiconductor substrate and the gate electrodes onto surfaces of the gate electrodes lying on a second impurity diffusion region side.

12. The nonvolatile storage device according to claim 11 ,

wherein the surfaces of the gate electrodes lying on the second impurity diffusion region side provided with the films stack thereon extend vertically to the semiconductor substrate.

13. The nonvolatile storage device according to claim 5 ,

wherein the charge accumulating layers are a silicon nitride film, a silicon oxynitride film, an alumina film, a hafnium silicate film, a hafnium oxide silicate film, or an aluminum silicate film, and

the tunnel insulating films are a silicon oxide film or a silicon oxynitride film.

14. The nonvolatile storage device according to claim 5 ,

wherein the film stacks further include an insulating film B on the charge accumulating layers provided on the tunnel insulating films, and

the insulating films B are a silicon oxide film or a silicon oxynitride film.

15. A nonvolatile storage device, comprising:

a semiconductor substrate;

a first gate electrode and a second gate electrode provided on the semiconductor substrate;

an impurity diffusion region A provided in the semiconductor substrate so as to be sandwiched between the first gate electrode and the second gate electrode;

an impurity diffusion region B provided in the semiconductor substrate so as to be opposed to the impurity diffusion region A and sandwich the first gate electrode between the impurity diffusion regions A and B;

an impurity diffusion region C provided in the semiconductor substrate so as to be opposed to the impurity diffusion region A and sandwich the second gate electrode between the impurity diffusion regions A and C; and

a film stack (I) or (II),

wherein the film stack (I) comprises:

a film stack extending from between the semiconductor substrate and the first gate electrode onto a surface of the first gate electrode lying on an impurity diffusion region A side, being in contact with the impurity diffusion region A, and including a charge accumulating layer and a tunnel insulating film sequentially from a first gate electrode side; and

a film stack extending from between the semiconductor substrate and the second gate electrode onto a surface of the second gate electrode lying on an impurity diffusion region A side, being in contact with the impurity diffusion region A, and including a charge accumulating layer and a tunnel insulating film sequentially from a second gate electrode side, and

the film stack (II) comprises:

a film stack extending from between the semiconductor substrate and the first gate electrode onto a surface of the first gate electrode lying on an impurity diffusion region B side, being in contact with the impurity diffusion region B, and including a charge accumulating layer and a tunnel insulating film sequentially from the first gate electrode side; and

a film stack extending from between the semiconductor substrate and the second gate electrode onto a surface of the second gate electrode lying on an impurity diffusion region C side, being in contact with the impurity diffusion region C, and including a charge accumulating layer and a tunnel insulating film sequentially from the second gate electrode side.

16. The nonvolatile storage device according to claim 15 ,

wherein surfaces (A) or (B) provided with the film stack thereon extends vertically to the semiconductor substrate,

the surfaces (A) including the surface of the first gate electrode and the surface of the second gate electrode lying on the impurity diffusion region A side, and

the surfaces (B) including the surface of the first gate electrode lying on the impurity diffusion region B side and the surface of the second gate electrode lying on the impurity diffusion region C side.

17. The nonvolatile storage device according to claim 15 ,

wherein among the impurity diffusion region A, and the impurity diffusion regions B and C, impurity diffusion region provided with the film stack thereon is deeper than impurity diffusion region not provided with the film stack thereon in a thickness direction of the semiconductor substrate.

18. The nonvolatile storage device according to claim 15 ,

wherein the charge accumulating layer is a silicon nitride film, a silicon oxynitride film, an alumina film, a hafnium silicate film, a hafnium oxide silicate film, or an aluminum silicate film, and

the tunnel insulating film is a silicon oxide film or a silicon oxynitride film.

19. The nonvolatile storage device according to claim 15 ,

wherein the film stack further includes an insulating film B on the charge accumulating layer provided on the tunnel insulating film, and

the insulating film B is a silicon oxide film or a silicon oxynitride film.