FinFET structure and methods thereof

1. A method of semiconductor device fabrication, comprising:

providing a substrate including a fin extending therefrom, wherein the fin includes a channel region, and source and drain regions adjacent to and on either side of the channel region, and wherein a gate structure is disposed over the channel region;

forming a first epitaxial layer at least partially embedded within the source and drain regions;

forming a dielectric layer over the first epitaxial layer;

etching the dielectric layer to form first and second openings that at least partially expose a top surface of the first epitaxial layer in the source region and the drain region respectively;

depositing a second epitaxial layer over, and in contact with, the top surface of the first epitaxial layer, wherein the first and second epitaxial layers provide cascaded source and drain epitaxial features in each of the source and drain regions; and

forming a silicide layer over, and in contact with, the second epitaxial layer.

2. The method of claim 1 , wherein the first opening is larger than the second opening.

3. The method of claim 1 , further comprising prior to etching the dielectric layer, forming a protective sacrificial layer over the gate structure.

4. The method of claim 1 , wherein the etching the dielectric layer exposes the top surface of the first epitaxial layer in at least two physically separated and adjacent fins, and wherein the depositing the second epitaxial layer serves to form a single, merged epitaxial region in at least one of the source and drain regions.

5. The method of claim 2 , wherein the second epitaxial layer has a larger surface area in the source region than in the drain region.

6. The method of claim 5 , wherein the silicide layer has a larger surface area in the source region than in the drain region.

7. The method of claim 1 , wherein the gate structure includes a metal layer, and wherein a top surface of the second epitaxial layer is higher than a top surface of the metal layer along a direction normal to the substrate.

8. The method of claim 1 , further comprising:

after depositing the second epitaxial layer, performing a pre-amorphization implant (PAI) into the second epitaxial layer.

9. The method of claim 8 , further comprising:

after performing the PAI, depositing a metal layer over the second epitaxial layer; and

performing an annealing process to form the silicide layer over, and in contact with, the second epitaxial layer.

10. The method of claim 1 , wherein the channel region includes a first material, and wherein the first epitaxial layer includes a second material different than the first material.

11. The method of claim 8 , wherein the first epitaxial layer applies stress to the channel region, and further comprising performing the PAI into the second epitaxial layer without relaxation of the applied stress to the channel region.

12. A method, comprising:

providing a substrate including a fin extending therefrom, wherein the fin includes a channel region, and source and drain regions adjacent to and on either side of the channel region, and wherein a gate structure is disposed over the channel region, the gate structure including a metal layer;

forming a first epitaxial layer at least partially embedded within the source and drain regions, wherein the first epitaxial layer stresses the channel region;

forming a second epitaxial layer over, and in contact with, the first epitaxial layer, wherein the second epitaxial layer has a larger surface area in the source region than in the drain region, and wherein a top surface of the second epitaxial layer is higher than a top surface of the metal layer along a direction normal to the substrate; and

forming a silicide layer over, and in contact with, the second epitaxial layer.

13. The method of claim 12 , further comprising:

prior to forming the second epitaxial layer, forming a first dielectric layer over the first epitaxial layer; and

etching the first dielectric layer to form first and second openings that at least partially expose a top surface of the first epitaxial layer in the source region and the drain region respectively.

14. The method of claim 13 , further comprising:

after forming the silicide layer, forming a second dielectric layer over the silicide layer;

patterning the second dielectric layer to form contact openings exposing the silicide layer and depositing a contact metal within the contact openings and in contact with the silicide layer;

forming a third dielectric layer over the contact metal; and

patterning the third dielectric layer to form via openings exposing the contact metal and depositing a via metal within the via openings and in contact with the contact metal.

15. The method of claim 12 , further comprising:

after forming the second epitaxial layer, performing a pre-amorphization implant (PAI) into the second epitaxial layer.

16. The method of claim 15 , further comprising:

after performing the PAI, depositing another metal layer over the second epitaxial layer; and

performing an annealing process to form the silicide layer over, and in contact with, the second epitaxial layer.

17. The method of claim 12 , wherein the channel region includes a first material, and wherein the first epitaxial layer includes a second material different than the first material.

18. The method of claim 15 , further comprising performing the PAI into the second epitaxial layer without relaxation of the stress to the channel region.

19. The method of claim 13 , further comprising prior to etching the first dielectric layer, forming a sacrificial helmet layer over the gate structure.

20. The method of claim 19 , further comprising prior to forming the sacrificial helmet layer, performing a pull-back process of a nitride layer overlying the gate structure and of a sidewall spacer formed on a sidewall of the gate structure.