FinFET design with reduced current crowding

1. An integrated circuit structure comprising:

a substrate;

insulation regions over the substrate; and

a fin field-effect transistor (FinFET) comprising:

a plurality of fins over the substrate, wherein each of the plurality of fins comprises a first fin portion and a second fin portion;

a gate stack on a top surface and sidewalls of the first fin portion of each of the plurality of fins;

an epitaxial semiconductor layer comprising a portion directly over the second fin portion of each of the plurality of fins, and sidewall portions directly over the insulation regions;

a silicide layer on, and having an interface with, the epitaxial layer, wherein a peripheral ratio of a total length of an effective silicide peripheral of the FinFET to a total length of peripherals of the plurality of fins is greater than 1; and

a dummy fin, wherein the epitaxial semiconductor layer extends on a top surface and sidewalls of the dummy fin, and wherein the effective silicide peripheral does not comprise any sidewall portion on outer sides of the dummy fin.

2. The integrated circuit structure of claim 1 , wherein the peripheral ratio is greater than about 1.1.

3. The integrated circuit structure of claim 1 , wherein the effective silicide peripheral comprises sidewall portions on outer sidewalls of the plurality of fins.

4. The integrated circuit structure of claim 1 , further comprising a dummy fin, wherein the epitaxial semiconductor layer extends on a top surface and sidewalls of the dummy fin, and wherein the effective silicide peripheral comprises no sidewall portion on an outer side of the dummy fin.

5. The integrated circuit structure of claim 1 , wherein a top portion of the effective silicide peripheral over the plurality of fins is substantially flat.

6. The integrated circuit structure of claim 1 , wherein a top portion of the effective silicide peripheral over the plurality of fins is not flat.

7. The integrated circuit structure of claim 1 , wherein a top surface of the silicide layer is flat.

8. An integrated circuit structure comprising:

a substrate;

insulation regions over the substrate; and

a fin field-effect transistor (FinFET) comprising:

a plurality of fins over the substrate, wherein each of the plurality of fins comprises a first fin portion and a second fin portion;

a gate stack on a top surface and sidewalls of the first fin portion of each of the plurality of fins;

an epitaxial semiconductor layer comprising a portion directly over the second fin portion of each of the plurality of fins, and sidewall portions directly over the insulation regions;

a silicide layer on, and having an interface with, the epitaxial layer, wherein a peripheral ratio of a total length of an effective silicide peripheral of the FinFET to a total length of peripherals of the plurality of fins is greater than 1, and wherein the effective silicide peripheral and the fin peripheral each have a different cross sectional profile shape at a same position along a length of the plurality of fins; and

a dummy fin covered by the epitaxial semiconductor layer, and wherein outer sidewall portions from the dummy fin do not contribute to an effective silicide peripheral of the FinFET.

9. The integrated circuit structure of claim 8 , wherein the peripheral ratio is greater than about 1.1.

10. The integrated circuit structure of claim 8 , wherein the effective silicide peripheral comprises sidewall portions on outer sidewalls of the plurality of fins.

11. The integrated circuit structure of claim 8 , further comprising a dummy fin, wherein the epitaxial semiconductor layer extends on a top surface and sidewalls of the dummy fin, and wherein the effective silicide peripheral comprises no sidewall portion on an outer side of the dummy fin.

12. The integrated circuit structure of claim 8 , wherein a top portion of the effective silicide peripheral over the plurality of fins is substantially flat.

13. The integrated circuit structure of claim 8 , wherein a top portion of the effective silicide peripheral over the plurality of fins is not flat.

14. The integrated circuit structure of claim 8 , wherein a top surface of the silicide layer is flat.

15. An integrated circuit structure comprising:

a substrate;

insulation regions over the substrate; and

a fin field-effect transistor (FinFET) comprising:

a plurality of fins over the substrate, wherein each of the plurality of fins comprises a first fin portion and a second fin portion;

a gate stack on a top surface and sidewalls of the first fin portion of each of the plurality of fins;

an epitaxial semiconductor layer comprising a portion directly over the second fin portion of each of the plurality of fins, and sidewall portions directly over the insulation regions;

a silicide layer on, and having an interface with, the epitaxial layer, wherein a peripheral ratio of a total length of an effective silicide peripheral of the FinFET to a total length of peripherals of the plurality of fins is greater than 1, and wherein the effective silicide peripheral and the fin peripheral each have a different cross sectional profile shape in a same plane; and

a dummy fin covered by the epitaxial semiconductor layer, and wherein outer sidewall portions from the dummy fin do not contribute to an effective silicide peripheral of the FinFET.

16. The integrated circuit structure of claim 15 , wherein the peripheral ratio is greater than about 1.1.

17. The integrated circuit structure of claim 15 , wherein the peripheral ratio is between about 1.1 and 1.4.

18. The integrated circuit structure of claim 15 , wherein a top portion of the effective silicide peripheral over the plurality of fins is substantially flat.

19. The integrated circuit structure of claim 15 , wherein a top portion of the effective silicide peripheral over the plurality of fins is not flat.

20. The integrated circuit structure of claim 15 , wherein the silicide layer is conformal.