Method for manufacturing semiconductor fin structure with extending gate structure

1. A method for manufacturing a semiconductor structure, comprising:

forming a fin structure protruding from a substrate;

forming an isolation structure around the fin structure over the substrate;

forming a dummy gate structure across the fin structure, the dummy gate structure including a dummy gate dielectric layer and a dummy gate electrode layer, and sidewall spacers such that a part of the dummy gate dielectric layer is disposed between at least one of the sidewall spacers and the isolation structure;

removing the dummy gate dielectric layer except for the part of the dummy gate dielectric layer and the dummy gate electrode layer to form a trench between the sidewall spacers;

removing a portion of the isolation structure to form an extended trench extending into the isolation structure; and

forming a gate structure in the extended trench, wherein:

a portion of the extended trench further extends to a position below the sidewall spacers, and

after the gate structure is formed, the part of the dummy gate dielectric layer remains, and the gate structure is in contact with the part of the dummy gate dielectric layer and the sidewall spacers.

2. The method of claim 1 , wherein a portion of the sidewall spacers is positioned over the isolation structure and has a first height and a portion of the gate structure is positioned over the isolation structure and has a second height which is greater than the first height.

3. The method of claim 1 , wherein:

the dummy gate electrode is formed on a first portion of the dummy gate dielectric layer and the sidewall spacers are formed on a second portion of the dummy gate dielectric layer,

the first portion of the dummy gate dielectric layer is removed, and

the second portion of the dummy gate dielectric layer remains and is in direct contact with the gate structure.

4. The method of claim 3 , wherein, in the removing a portion of the isolation structure, a part of the second portion of the dummy gate dielectric layer is removed.

5. The method of claim 1 , wherein the forming the gate structure in the trench further comprises:

depositing a gate dielectric layer over a bottom surface and sidewalls of the trench;

depositing a work function metal layer over the gate dielectric layer; and

depositing a metal gate electrode layer over the work function metal layer.

6. The method of claim 5 , wherein the gate dielectric layer is in contact with the part of the dummy gate dielectric layer and the sidewall spacers.

7. The method of claim 5 , wherein a part of the work function metal layer is located below the sidewall spacers.

8. The method of claim 7 , wherein a part of the metal gate electrode layer is located below the sidewall spacers.

9. The method of claim 1 , wherein after the trench is formed, a bottom of the trench is in contact with the fin structure.

10. The method of claim 1 , wherein the gate structure comprises a first portion formed over the fin structure and a second portion formed over the isolation structure, and the second portion of the gate structure comprises an extending portion extending into the isolation structure.

11. The method of claim 10 , wherein the extending portion of the second portion of the gate structure has a thickness in a range from 10 Å to 2000 Å.

12. The method of claim 10 , wherein the sidewall spacers do not extend into the isolation structure.

13. The method of claim 12 , wherein a bottom surface of the spacer is not level with a bottom surface of the second portion of the gate structure over the isolation structure.

14. The method of claim 12 , wherein the spacer has a first height, and the second portion of the gate structure has a second height which is greater than the first height.

15. The method of claim 10 , wherein the first portion of the gate structure has a first width, and the extending portion of the second portion of the gate structure has a second width which is greater than the first width.

16. The method of claim 15 , wherein a difference between the first width and the second width is in a range from 5 Å to 200 Å.

17. A method for manufacturing a semiconductor device, comprising:

forming a fin structure protruding from a substrate;

forming an isolation insulating layer around the fin structure over the substrate;

forming a dummy gate structure across the fin structure, the dummy gate structure including a dummy gate dielectric layer and a dummy gate electrode layer, and sidewall spacers such that a part of the dummy gate dielectric layer is disposed between at least one of the sidewall spacers and the isolation structure;

forming an interlayer dielectric layer disposed at both vertical sides of the sidewall insulating layers;

removing the dummy gate electrode layer and the dummy gate dielectric layer except for the part of the dummy gate dielectric layer so that a space is created;

etching the a surface of the isolation insulating layer in the space so as to form a recess; and

forming a gate structure in the space and the recess,

wherein, after the gate structure is formed, the part of the dummy gate dielectric layer remains, and the gate structure is in direct contact with part of the dummy gate dielectric layer and the sidewall spacers.

18. The method of claim 17 , wherein a depth of the recess from a level of a bottom surface of the sidewall insulating layers is in a range of 1 nm to 200 nm.

19. The method of claim 17 , wherein a portion of the recess further extends to a position below the sidewall spacers.

20. A method for manufacturing a fin field effect transistor, comprising:

forming a fin structure over a substrate;

forming an isolation structure around the fin structure over the substrate;

forming a first dielectric layer;

after the first dielectric layer is formed, forming a dummy gate structure across the fin structure;

forming sidewall spacers on sidewalls of the dummy gate structure such that a part of the first dielectric layer is disposed between at least one of the sidewall spacers and the isolation structure;

forming a second dielectric layer on the sidewall spacers and on the isolation structure;

forming an interlayer dielectric layer on the second dielectric layer;

removing the dummy gate structure and the first dielectric layer except for the part of the first dielectric layer to form a trench between the sidewall spacers;

removing a portion of the isolation structure to form an extended trench extending into the isolation structure; and

forming a gate structure in the extended trench, wherein:

a portion of the extended trench further extends to a position below the sidewall spacers,

after the gate structure is formed, the part of the first dielectric layer remains,

the sidewall spacers and the first dielectric layer are made of different materials, and

the sidewall spacers are in direct contact with the gate structure.