Nonvolatile semiconductor storage device with charge storage layer and its manufacturing method

1. A nonvolatile semiconductor storage device, comprising:

a semiconductor substrate;

a charge storage layer formed above the semiconductor substrate;

a control gate formed above the charge storage layer;

a silicide layer formed above the control gate;

a word gate formed above a side of the control gate; and

a side wall formed beside the control gate at an opposite side of the word gate,

wherein a top surface of the silicide layer is substantially flat,

wherein the word gate covers other than the control gate, and

wherein a height of the side wall is more than a height of the silicide layer.

2. The nonvolatile semiconductor storage device according to claim 1 , wherein the silicide layer comprising a first silicide layer, the nonvolatile semiconductor storage device further comprising a second silicide layer formed on the word gate.

3. The nonvolatile semiconductor storage device according to claim 1 , wherein a height of the word gate is higher than a height of the control gate.

4. The nonvolatile semiconductor storage device according to claim 1 , wherein the charge storage layer includes:

a first silicon oxide layer;

a silicon nitride layer formed above the first silicon oxide layer; and

a second silicon oxide layer formed above the silicon nitride layer.

5. The nonvolatile semiconductor storage device according to claim 1 , further comprising:

a first diffusion layer formed on the semiconductor substrate; and

a second diffusion layer formed on the semiconductor substrate,

wherein the charge storage layer and the word gate are disposed between the first diffusion layer and the second diffusion layer.

6. The nonvolatile semiconductor storage device according to claim 5 , wherein the silicide layer comprises a first silicide layer, the nonvolatile semiconductor storage device further comprising:

a second silicide layer formed on the word gate;

a third silicide layer formed on the first diffusion layer; and

a fourth silicide layer formed on the second diffusion layer.

7. The nonvolatile semiconductor storage device according to claim 1 , wherein the silicide layer contacts an upper surface of the control gate.

8. The nonvolatile semiconductor storage device according to claim 1 , further comprising:

another silicide layer disposed on an upper surface of the word gate.

9. The nonvolatile semiconductor storage device according to claim 1 , wherein the word gate does not overlap the control gate.

10. A nonvolatile semiconductor storage device, comprising:

a semiconductor substrate;

a first charge storage layer formed above the semiconductor substrate;

a second charge storage layer formed above the semiconductor substrate;

word gate formed between the first charge storage layer and the second charge storage layer;

a first control gate formed above the first charge storage layer;

a second control gate formed above the second charge storage layer;

a first silicide layer formed above the first control gate;

a second silicide layer formed above the second control gate;

a first side wall formed beside the first control gate at an opposite side of the word gate; and

a second side wall formed beside the second control gate at an opposite side of the word gate,

wherein a top surface of the first silicide layer is substantially flat,

wherein the word gate covers other than the first control gate and the second control gate,

wherein a height of the first side wall is more than a height of the first silicide layer, and

wherein a height of the second side wall is more than a height of the second silicide layer.

11. The nonvolatile semiconductor storage device according to claim 10 , wherein the first charge layer and the second charge layer are disposed symmetrically with respect to the word gate,

wherein the first control gate and the second control gate are disposed symmetrically with respect to the word gate, and

wherein the first silicide layer and the second silicide layer are disposed symmetrically with respect to the word gate.

12. The nonvolatile semiconductor storage device according to claim 10 , further comprising a third silicide layer formed on the word gate.

13. The nonvolatile semiconductor storage device according to claim 10 , wherein a height of the word gate is higher than a height of the first control gate and the second control gate.

14. The nonvolatile semiconductor storage device according to claim 10 , wherein the first charge storage layer includes:

first silicon oxide layer;

a first silicon nitride layer formed above the first silicon oxide layer; and

a second silicon oxide layer formed above the first silicon nitride layer, and

wherein the second charge storage layer includes:

a third silicon oxide layer;

a second silicon nitride layer formed above the third silicon oxide layer; and

a fourth silicon oxide layer formed above the second silicon nitride layer.

15. The nonvolatile semiconductor storage device according to claim 10 , further comprising:

a first diffusion layer formed on the semiconductor substrate; and

a second diffusion layer formed on the semiconductor substrate,

wherein the first charge storage layer, the second charge storage layer and the word gate are disposed between the first diffusion layer and the second diffusion layer.

16. The nonvolatile semiconductor storage device according to claim 15 , further comprising:

a third silicide layer formed on the word gate;

a fourth silicide layer formed on the first diffusion layer; and

a fifth silicide layer formed on the second diffusion layer.

17. The nonvolatile semiconductor storage device according to claim 10 , wherein the first silicide layer contacts an upper surface of the first control gate, and

wherein the second silicide layer contacts an upper surface of the second control gate.

18. The nonvolatile semiconductor storage device according to claim 10 , wherein the word gate does not overlap the first control gate and the second control gate.

19. The nonvolatile semiconductor storage device according to claim 10 , wherein an entirety of the word gate is confined between the first control gate and the second control gate.

20. The nonvolatile semiconductor storage device according to claim 10 , wherein the word gate covers other than the first charge storage layer and the second charge storage layer.