Semiconductor device and manufacturing method thereof

1. A method, comprising:

forming a dummy gate structure over a substrate;

forming a source/drain structure over the substrate;

replacing the dummy gate structure with a metal gate structure;

forming a protection cap over the metal gate structure;

forming a source/drain contact over the source/drain structure;

performing a selective deposition process to form a first etch stop layer on the protection cap, wherein the selective deposition process has a faster deposition rate on the protection cap than on the source/drain contact;

depositing a second etch stop layer over the first etch stop layer and the source/drain contact;

forming an interlayer dielectric (ILD) layer over the second etch stop layer;

etching the ILD layer and the second etch stop layer to form an opening; and

forming a via contact in the opening.

2. The method of claim 1 , further comprising depositing a metal cap on a top surface of the source/drain contact prior to depositing the second etch stop layer, while keeping a top surface of the first etch stop layer uncovered.

3. The method of claim 1 , further comprising etching back the source/drain contact after depositing the first etch stop layer selectively on the protection cap.

4. The method of claim 1 , wherein depositing the second etch stop layer is performed using a non-selective deposition process.

5. The method of claim 1 , wherein the selective deposition process is performed such that a top surface of the source/drain contact is free from the first etch stop layer.

6. A method, comprising:

forming a gate structure over a substrate;

forming gate spacers on opposite sidewalls of the gate structure;

forming source/drain structures over the substrate and on opposite sides of the gate structure;

forming a source/drain contact over one of the source/drain structures;

forming a protection cap over the gate structure and the gate spacers;

forming a first etch stop layer over the protection cap;

after forming the first etch stop layer, etching back the source/drain contact to expose a sidewall of the protection cap; and

forming a via contact in contact with the sidewall of the protection cap and a sidewall of the first etch stop layer.

7. The method of claim 6 , wherein forming the first etch stop layer comprises performing a selective deposition process, such that a top surface of the source/drain contact is free from the first etch stop layer.

8. The method of claim 6 , further comprising forming a second etch stop layer in contact with the first etch stop layer using a non-selective deposition process.

9. The method of claim 6 , further comprising:

prior to forming the via contact, forming a second etch stop layer over the first etch stop layer and covering the sidewall of the protection cap;

forming an interlayer dielectric (ILD) layer over the second etch stop layer; and

performing an etching process to remove portions of the second etch stop layer and the ILD layer to expose the sidewall of the protection cap.

10. The method of claim 9 , wherein the etching process is performed such that a portion of the first etch stop layer is thinned.

11. The method of claim 9 , wherein forming the second etch stop layer is performed such that a bottommost surface of the second etch stop layer is lower than a bottommost surface of the first etch stop layer.

12. The method of claim 6 , further comprising etching back the gate structure prior to forming the protection cap.

13. The method of claim 6 , further comprising etching back the gate spacers after etching back the gate structure and prior to forming the protection cap.

14. A method, comprising:

forming a gate structure over a substrate;

forming gate spacers on opposite sidewalls of the gate structure;

forming source/drain structures over the substrate and on opposite sides of the gate structure;

forming a source/drain contact over one of the source/drain structures;

forming a first etch stop layer over the gate structure;

after forming the first etch stop layer, selectively forming a metal cap over the source/drain contact, wherein the metal cap has a higher deposition rate on the source/drain contact than on the first etch stop layer; and

forming a via contact over the metal cap and the first etch stop layer.

15. The method of claim 14 , further comprising:

forming a second etch stop layer over the first etch stop layer;

forming an interlayer dielectric (ILD) layer over the second etch stop layer; and

etching the second etch stop layer and the ILD layer to form an opening, wherein the via contact is formed in the opening.

16. The method of claim 15 , wherein etching the second etch stop layer and the ILD layer further comprises etching the first etch stop layer such that the metal cap protrudes from a top surface of the first etch stop layer.

17. The method of claim 16 , wherein the via contact is formed in contact with a sidewall of the metal cap.

18. The method of claim 14 , further comprising etching back the source/drain contact such that a top surface of the source/drain contact is lower than top surfaces of the gate spacers.

19. The method of claim 14 , further comprising forming a protection cap over the gate structure prior to forming the first etch stop layer, wherein the forming the first etch stop layer comprises performing a selective deposition process, such that a top surface of the source/drain contact is free from the first etch stop layer.

20. The method of claim 1 , wherein etching the ILD layer and the second etch stop layer is performed such that a portion of the first etch stop layer is etched.