Semiconductor device and manufacturing method thereof
A semiconductor device includes a substrate; at least one source/drain feature at least partially disposed in the substrate; an isolation structure disposed on the substrate and includes a first portion; a gate structure disposed on the first portion of the isolation structure and adjacent to the source/drain feature; and at least one gate spacer disposed on a sidewall of the gate structure, in which a top surface of the first portion of the isolation structure is in contact with the gate structure and is higher than a bottommost surface of the gate spacer.
1. A semiconductor device, comprising:
a substrate;
at least one source/drain feature at least partially disposed in the substrate;
an isolation structure disposed on the substrate and comprises a first portion;
a gate structure disposed on the first portion of the isolation structure and adjacent to the source/drain feature; and
at least one gate spacer disposed on a sidewall of the gate structure,
wherein a top surface of the first portion of the isolation structure is in contact with the gate structure and is higher than a bottommost surface of the gate spacer;
wherein the gate spacer includes an upper portion and a lower portion;
wherein an inner sidewall of the upper portion and an inner sidewall of the lower portion form an angle therebetween; and
wherein the inner sidewall of the lower portion tapers away from the source/drain feature.
2. The semiconductor device of claim 1 , wherein the isolation structure further comprises a second portion adjacent to the first portion of the isolation structure and the source/drain feature, and the top surface of the first portion of the isolation structure is higher than a top surface of the second portion of the isolation structure.
3. The semiconductor device of claim 2 , wherein the top surface of the first portion of the isolation structure and the top surface of the second portion of the isolation structure are concave.
4. The semiconductor device of claim 1 , wherein the gate spacer has a multi-layer configuration.
5. The semiconductor device of claim 1 , wherein the gate spacer comprises:
a first dielectric layer in contact with the gate structure; and
a second dielectric layer and a third dielectric layer, wherein the second dielectric layer is disposed between the first dielectric layer and the third dielectric layer, wherein a bottom surface of the second dielectric layer is higher than a bottom surface of the first dielectric layer and a bottom surface of the third dielectric layer.
6. The semiconductor device of claim 1 , wherein the gate structure has a notched portion in contact with the first portion of the isolation structure.
7. The semiconductor device of claim 1 , wherein the sidewall of the gate structure is adjacent the source/drain feature.
8. A semiconductor device, comprising:
a substrate having at least one fin structure, wherein the fin structure has a channel portion and at least one source/drain portion adjacent to the channel portion;
an isolation structure disposed on the substrate and comprises a first portion adjacent to the channel portion of the fin structure;
a gate structure disposed on the first portion of the isolation structure and the channel portion of the fin structure and having substantially the same width as the first portion of the isolation structure; and
two gate spacers respectively disposed on opposite sidewalls of the gate structure,
wherein a part of the first portion of the isolation structure is disposed between the gate spacers;
wherein at least one of the gate spacers comprises a first dielectric layer, a second dielectric layer, and a third dielectric layer;
wherein the second dielectric layer is between the first and third dielectric layers; and
wherein a bottom surface of the second dielectric layer is above a bottom surface of the first dielectric layer and a bottom surface of the third dielectric layer.
9. The semiconductor device of claim 8 , wherein the isolation structure further comprises a second portion adjacent to the first portion of the isolation structure and the source/drain portion of the fin structure, and a top surface of the first portion of the isolation structure is higher than a top surface of the second portion of the isolation structure.
10. The semiconductor device of claim 9 , wherein the top surface of the first portion of the isolation structure and the top surface of the second portion of the isolation structure are curved.
11. The semiconductor device of claim 8 , wherein the first portion of the isolation structure is in contact with a sidewall of at least one of the gate spacers.
12. The semiconductor device of claim 11 , wherein a height of the first portion of the isolation structure is greater than a height of a second portion of the isolation structure.
13. The semiconductor device of claim 8 , wherein the part of the first portion of the isolation structure disposed between the gate spacers has a tapered profile.
14. The semiconductor device of claim 8 , wherein the part of the first portion of the isolation structure disposed between the gate spacers has a notched profile.
15. The semiconductor device of claim 8 , wherein the inner sidewall of the upper portion of the gate spacer is substantially perpendicular to a top surface of the substrate.
16. A method for manufacturing a semiconductor device, comprising:
forming at least one fin structure on a substrate;
forming an isolation structure on the substrate and adjacent to the fin structure;
forming a gate structure on the fin structure and the isolation structure;
recessing the isolation structure uncovered by the gate structure to form first and second portions of the isolation structure, wherein a top surface of the second portion is below a top surface of the first portion;
after recessing the isolation structure, forming two gate spacers respectively on opposite sidewalls of the gate structure and on the second portion of the isolation structure; and
after recessing the isolation structure and forming the two gate spacers, performing a first cleaning process to the second portion of the isolation structure such that a bottom surface of at least one of the gate spacers is separated from the second portion of the isolation structure.
17. The method of claim 16 , further comprising:
removing the gate structure; and
performing a second cleaning process to the first portion of the isolation structure between the gate spacers.
18. The method of claim 16 , wherein recessing the isolation structure comprises tuning a profile of the first portion of the isolation structure.
19. The method of claim 18 , wherein tuning the profile of the first portion of the isolation structure comprises:
performing an anisotropic etching process to the isolation structure uncovered by the gate structure; and
performing an isotropic etching process to the isolation structure uncovered by the gate structure after performing the anisotropic etching process.
20. The method of claim 18 , wherein the tuning the profile of the first portion of the isolation structure comprises performing an isotropic etching process to the isolation structure uncovered by the gate structure.