FinFET contact structure and method for forming the same

1. A method comprising:

epitaxially growing a first semiconductor material to form a first drain/source region and a second drain/source region in a semiconductor substrate;

applying a first etching process to top surfaces of the first drain/source region and the second drain/source region and forming a first recess in the first drain/source region and a second recess in the second drain/source region as a result of the first etching process, wherein the first drain/source region and the second drain/source region have concave surfaces as a result of the first etching process; and

forming a first drain/source contact and a second drain/source contact, wherein:

a bottom portion of the first drain/source contact is in the first recess; and

a bottom portion of the second drain/source contact is in the second recess.

2. The method of claim 1 , further comprising:

forming a first dislocation plane underlying the first drain/source region; and

forming a second dislocation plane underlying the second drain/source region, wherein the first dislocation plane is in parallel with the second dislocation plane.

3. The method of claim 2 , wherein:

prior to the step of epitaxially growing the first semiconductor material, forming a first gate structure over a semiconductor substrate, wherein the first drain/source region and the second drain/source region are on opposite sides of the first gate structure.

4. The method of claim 3 , further comprising:

forming a second gate structure over a semiconductor substrate;

epitaxially growing a second semiconductor material to form a third drain/source region and a fourth drain/source region in the semiconductor substrate, wherein the third drain/source region and the fourth drain/source region are on opposite sides of the second gate structure; and

applying the first etching process to top surfaces of the third drain/source region and the fourth drain/source region and forming recessed top surfaces of the third drain/source region and the fourth drain/source region as a result of the first etching process.

5. The method of claim 4 , wherein:

the first drain/source region, the second drain/source region and the first gate structure form an n-type transistor; and

the third drain/source region, the fourth drain/source region and the second gate structure form a p-type transistor.

6. The method of claim 1 , wherein:

the first recess and the second recess are formed in comprise middle-of-line (MEOL) processes performed after a front-end-of line (FEOL) process and before a back-end-of-line (BEOL) process.

7. The method of claim 1 , wherein:

a depth of the first recess is in a range from about 5 nm to about 25 nm; and

a depth of the second recess is in a range from about 5 nm to about 25 nm.

8. A method comprising:

epitaxially growing a first semiconductor material in a first portion of a substrate to form a first drain/source region and a second drain/source region;

epitaxially growing a second semiconductor material in a second portion of the substrate to form a third drain/source region and a fourth drain/source region, wherein the first portion and the second portion are separated by an isolation region;

applying an etching process to top surfaces of the first drain/source region, the second drain/source region, the third drain/source region and the fourth drain/source region and forming a first recess in the first drain/source region, a second recess in the second drain/source region, a third recess in the third drain/source region and a fourth recess in the fourth drain/source region as a result of the etching process, wherein the first drain/source region, the second drain/source region, the third drain/source region and the fourth drain/source region have concave surfaces as a result of the etching process; and

forming a first drain/source contact, a second drain/source contact, a third drain/source contact and a fourth drain/source contact, wherein:

a bottom portion of the first drain/source contact is in the first recess;

a bottom portion of the second drain/source contact is in the second recess;

a bottom portion of the third drain/source contact is in the third recess; and

a bottom portion of the fourth drain/source contact is in the fourth recess.

9. The method of claim 8 , further comprising:

forming a first gate structure and a second gate structure over the substrate, wherein:

the first drain/source region and the second drain/source region are on opposite sides of the first gate structure; and

the third drain/source region and the fourth drain/source region are on opposite sides of the second gate structure.

10. The method of claim 9 , wherein:

the first drain/source region, the second drain/source region and the first gate structure form an n-type transistor; and

the third drain/source region, the fourth drain/source region and the second gate structure form a p-type transistor.

11. The method of claim 10 , further comprising:

forming a first trench and a second trench in the first portion of the substrate, wherein the first trench and the second trench are on opposite sides of the first gate structure;

applying a pre-amorphous implantation process to the first portion of the substrate;

depositing a first tensile film layer on sidewalls and bottoms of the first trench and the second trench; and

forming a first dislocation plane underlying the first trench and a second dislocation plane underlying the second trench using an anneal process.

12. The method of claim 8 , wherein:

bottoms of the first recess, the second recess, the third recess and the fourth recess are of a concave surface.

13. The method of claim 8 , wherein:

the first semiconductor material is silicon; and

the second semiconductor material is silicon germanium.

14. A method comprising:

epitaxially growing a first semiconductor material in a substrate to form a first drain/source region and a second drain/source region, wherein top surfaces of the first drain/source region and the second drain/source region are level with top surface of the substrate;

epitaxially growing a second semiconductor material in the substrate to form a third drain/source region and a fourth drain/source region, wherein top surfaces of the third drain/source region and the fourth drain/source region are level with top surface of the substrate;

applying an etching process to top surfaces of the first drain/source region, the second drain/source region, the third drain/source region and the fourth drain/source region, wherein as a result of the etching process, the first drain/source region, the second drain/source region, the third drain/source region and the fourth drain/source region have concave surfaces; and

forming a first drain/source contact, a second drain/source contact, a third drain/source contact and a fourth drain/source contact connected to the first drain/source region, the second drain/source region, the third drain/source region and the fourth drain/source region respectively, wherein at least a portion of each drain/source contact is below the top surface of the substrate.

15. The method of claim 14 , wherein:

the first drain/source region and the second drain/source region form an n-type transistor; and

the third drain/source region and the fourth drain/source region form a p-type transistor.

16. The method of claim 14 , further comprising:

forming a first trench and a second trench on opposite sides of a first gate structure;

depositing an oxide layer over the first trench, the second trench, the first gate structure and a second gate structure;

depositing a photoresist layer; and

removing the photoresist layer over the first trench, the second trench and the first gate structure.

17. The method of claim 16 , further comprising:

after the step of removing the photoresist layer, applying a pre-amorphous implantation process to the first trench and the second trench, wherein as a result of applying the pre-amorphous implantation process, a plurality of structurally amorphous structures are formed under the first trench and the second trench;

forming a tensile film layer over the oxide layer; and

applying an anneal process to form a first dislocation plane under the first trench and a second dislocation plane under the second trench.

18. The method of claim 17 , wherein:

the first dislocation plane and the second dislocation plane are parallel to each other.

19. The method of claim 17 , further comprising:

removing the oxide layer after forming the first dislocation plane and the second dislocation plane.

20. The method of claim 14 , wherein:

a width of an area occupied by the first drain/source contact is about 50% of a width of a top surface of the first drain/source region.