P-channel flash with enhanced band-to-band tunneling hot electron injection

1. A method comprising:

forming a dummy gate stack on a substrate;

forming a first layer of a narrow bandgap material on the substrate by selective epitaxial growth, on each side of the dummy gate stack;

forming spacers on the first layer;

forming raised source/drains;

removing the dummy gate stack, subsequent to forming the raised source/drains, forming a cavity between the spacers; and

forming a memory gate stack in the cavity recess etching the first layer, leaving only the portion under the spacers; forming a second layer, by selective epitaxial growth on the substrate, adjacent the first layer and to substantially the same thickness as the first layer; and subsequently forming the raised source/drains by deep source/drain implantation in the second layer, wherein forming the second layer of a wide bandgap material.

2. The method according to claim 1 , comprising forming the raised source/drains by deep source/drain implantation in the first layer.

3. The method according to claim 1 , comprising forming the raised source/drains by in situ doping the first layer during selective epitaxial growth.

4. The method according to claim 1 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer, by selective epitaxial growth on the substrate, adjacent the first layer and to substantially the same thickness as the first layer; and

forming the raised source/drains by in situ doping the layer during selective epitaxial growth of the second layer.

5. The method according to claim 1 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer by selective epitaxial growth on the substrate, adjacent each side of the dummy gate stack, to a thickness less than the thickness of the first layer;

forming a third layer by selective epitaxial growth on the second layer, the second and third layers having a total thickness substantially equal to the thickness of the first layer; and

subsequently forming the raised source/drains by deep source/drain implantation in the third layer.

6. The method according to claim 1 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer by selective epitaxial growth on the substrate, adjacent each side of the dummy gate stack, to a thickness less than the thickness of the first layer;

forming a third layer by selective epitaxial growth on the second layer, the second and third layers having a total thickness substantially equal to the thickness of the first layer; and

forming the raised source/drains by in situ doping the layer during selective epitaxial growth of the third layer.

7. A method comprising:

forming a dummy gate stack on a substrate;

forming a first layer of a narrow band gap material on the substrate by selective epitaxial growth, on each side of the dummy gate stack;

removing the dummy gate stack, forming a cavity;

forming a memory gate stack in the cavity to a height greater than the thickness of the first layer;

forming spacers, subsequent to forming the memory gate stack, on the first layer on each side of the memory gate stack; and

forming raised source/drains recess etching the first layer, leaving only the portion under the spacers; forming a second layer, by selective epitaxial growth on the substrate, adjacent the first layer and to substantially the same thickness as the first layer; and subsequently forming the raised source/drains by deep source/drain implantation in the second layer wherein forming the second layer of a wide band gap material.

8. The method according to claim 7 , comprising forming the raised source/drains by deep source/drain implantation in the first layer.

9. The method according to claim 7 , comprising forming the raised source/drains by in situ doping during selective epitaxial growth of the first layer.

10. The method according to claim 7 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer, by selective epitaxial growth on the substrate, adjacent the first layer and to substantially the same thickness as the first layer; and

forming the raised source/drains by in situ doping during selective epitaxial growth of the second layer.

11. The method according to claim 7 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer by selective epitaxial growth on the substrate and adjacent each side of the dummy gate structure, to a thickness less than the thickness of the first layer;

forming a third layer by selective epitaxial growth on the second layer, the second and third layers having a total thickness substantially equal to the thickness of the first layer; and

subsequently forming the raised source/drains by deep source/drain implantation in the third layer.

12. The method according to claim 11 , comprising forming the second layer of a wide band gap material.

13. The method according to claim 7 , comprising:

recess etching the first layer, leaving only the portion under the spacers;

forming a second layer by selective epitaxial growth on the substrate and adjacent each side of the dummy gate structure, to a thickness less than the thickness of the first layer;

forming a third layer by selective epitaxial growth on the second layer, the second and third layers having a total thickness substantially equal to the thickness of the first layer; and

forming the raised source/drains by in situ doping during selective epitaxial growth of the third layer.