FinFETs with contact-all-around

1. An integrated circuit structure comprising:

a semiconductor substrate;

a semiconductor fin over the semiconductor substrate;

a gate stack on a top surface and a sidewall of the semiconductor fin;

a source/drain region on a side of the gate stack; and

a contact plug encircling a first portion of the source/drain region.

2. The integrated circuit structure of claim 1 , wherein the source/drain region further comprises a second portion overlapped by the contact plug.

3. The integrated circuit structure of claim 2 , wherein both the first portion and the second portion of the source/drain region comprise silicon germanium.

4. The integrated circuit structure of claim 2 , wherein the first portion of the source/drain region comprises silicon germanium, and the second portion of the source/drain region comprises silicon, and wherein the second portion of the source/drain region is free from germanium.

5. The integrated circuit structure of claim 2 , wherein the second portion of the source/drain region is physically disconnected from the first portion of the source/drain region by the contact plug.

6. The integrated circuit structure of claim 2 further comprising insulation regions extending into the semiconductor substrate, wherein the second portion of the source/drain region is over top surfaces of the insulation regions.

7. The integrated circuit structure of claim 1 further comprising a silicide region encircling the first portion of the source/drain region.

8. An integrated circuit structure comprising:

a semiconductor substrate;

insulation regions extending into the semiconductor substrate, wherein the insulation regions comprise first top surfaces and second top surfaces lower than the first top surfaces;

a semiconductor fin over the first top surfaces of the insulation regions;

a gate stack on a top surface and sidewalls of the semiconductor fin; and

a source/drain region on a side of the gate stack, wherein the source/drain region comprises:

a first portion having opposite sidewalls that are substantially parallel to each other, wherein the first portion is lower than the first top surfaces and higher than the second top surfaces of the insulation regions; and

a second portion over the first portion, wherein the second portion is physically disconnected from the first portion.

9. The integrated circuit structure of claim 8 further comprising a contact plug, wherein a portion of the contact plug physically separates the first portion and the second portion of the source/drain region from each other.

10. The integrated circuit structure of claim 8 further comprising a silicide region comprising:

a first portion in contact with a stop surface and the opposite sidewalls of the first portion of the source/drain region; and

a second portion encircling the second portion of the source/drain region.

11. The integrated circuit structure of claim 8 , wherein the insulation regions comprise first portions on opposite sides of the semiconductor fin, with the first portions of the insulation regions having the first top surfaces.

12. The integrated circuit structure of claim 8 , wherein the insulation regions comprise second portions on opposite sides of the source/drain region, with the second portions of the insulation regions having the second top surfaces.

13. The integrated circuit structure of claim 8 , wherein the second portion of the source/drain region is wider than the first portion of the source/drain region.

14. The integrated circuit structure of claim 8 , wherein the second portion of the source/drain region comprises facets.

15. An integrated circuit structure comprising:

a semiconductor substrate;

a semiconductor fin over the semiconductor substrate;

a gate stack on a top surface and sidewalls of the semiconductor fin;

a source/drain region on a side of the gate stack, wherein the source/drain region comprises:

a first portion; and

a second portion over the first portion;

a silicide layer comprising:

a first portion overlapping, and contacting a top surface of, the first portion of the source/drain region; and

a second portion overlapped by, and contacting a bottom surface of, the second portion of the source/drain region; and

a contact plug, wherein a portion of the contact plug physically separates the first portion and the second portion of the silicide layer from each other.

16. The integrated circuit structure of claim 15 , wherein the second portion of the silicide layer extends from a first sidewall to a second sidewall of the second portion of the source/drain region, and wherein the first sidewall and the second sidewall are opposite sidewalls of the second portion of the source/drain region.

17. The integrated circuit structure of claim 15 , wherein the first portion of the silicide layer extends from a first sidewall to a second sidewall of the first portion of the source/drain region, and wherein the first sidewall and the second sidewall are opposite sidewalls of the first portion of the source/drain region.

18. The integrated circuit structure of claim 15 , wherein the first portion and the second portion of the source/drain region are connected to the semiconductor fin.

19. The integrated circuit structure of claim 15 further comprising insulation regions extending into the semiconductor substrate, wherein the insulation regions comprise first top surfaces and second top surfaces lower than the first top surfaces, and the first portion of the source/drain region is lower than the first top surfaces and higher than the second top surfaces of the insulation regions.

20. The integrated circuit structure of claim 15 , wherein the first portion of the silicide layer is directly overlapping, and directly contacting a top surface of, the first portion of the source/drain region, and the second portion of the silicide layer is directly overlapped by, and directly contacting, a bottom surface of, the second portion of the source/drain region.