Method for manufacturing semiconductor fin structure with extending gate structure

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

forming a fin structure over a substrate;

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

forming a dielectric layer;

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

forming spacers on sidewalls of the dummy gate structure;

removing the dummy gate structure to form a trench between the 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, after the gate structure is formed, the dielectric layer is disposed between the spacers and the isolation structure, and the gate structure is in direct contact with the dielectric layer and the spacers.

2. The method for manufacturing a semiconductor structure as claimed in claim 1 , wherein a portion of the spacer 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 for manufacturing a semiconductor structure as claimed in claim 1 , wherein:

after the spacers are formed and before the dummy gate structure is removed, the dummy gate structure is formed on a first portion of the dielectric layer and the spacers are formed on a second portion of the dielectric layer,

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

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

4. The method for manufacturing a semiconductor structure as claimed in claim 3 , further comprising

removing a portion of the second portion after the dummy gate structure is removed.

5. The method for manufacturing a semiconductor structure as claimed in claim 1 , wherein a portion of the extended trench further extends to a position below the spacers.

6. The method for manufacturing a semiconductor structure as claimed in claim 1 , wherein the forming a 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.

7. The method for manufacturing a semiconductor structure as claimed in 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.

8. The method for manufacturing a semiconductor structure as claimed in claim 7 , wherein the extending portion of the second portion of the gate structure has a thickness in a range from about 10 Å to about 2000 Å.

9. The method for manufacturing a semiconductor structure as claimed in claim 7 , wherein the spacers do not extend into the isolation structure.

10. The method for manufacturing a semiconductor structure as claimed in claim 9 , 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.

11. The method for manufacturing a semiconductor structure as claimed in claim 9 , 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.

12. The method for manufacturing a semiconductor structure as claimed in claim 7 , 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.

13. The method for manufacturing a semiconductor structure as claimed in claim 12 , wherein a difference between the first width and the second width is in a range from about 5 Å to about 200 Å.

14. The method for manufacturing a semiconductor structure as claimed in claim 7 , wherein the gate structure has a bottom surface that is substantially a same level with or lower than a bottom surface of the fin structure.

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

forming a fin structure over a substrate, the fin structure extending in a first direction, an upper portion of the fin structure being exposed from an isolation insulating layer and a lower portion of the fin structure being embedded in the isolation insulating layer;

forming a dielectric layer over the fin structure and the isolation insulating layer;

after the dielectric layer is formed, forming a dummy electrode structure over the upper portion of the fin structure located above the lower portion of the fin structure, the dummy electrode structure including a dummy electrode layer, sidewall insulating layers disposed at both vertical sides of the dummy electrode layer, the dummy electrode structure being disposed over the isolation insulating layer;

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

removing the dummy electrode layer so that a space is created;

etching the dielectric layer and 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 dielectric layer is disposed between the sidewall insulating layers and the isolation insulating layer, and the gate structure is in direct contact with the dielectric layer and the sidewall insulating layers.

16. The method of claim 15 , wherein a depth of the recess from a level of a bottom surface of the sidewall insulating layers or a bottom surface of the interlayer dielectric layers is in a range of 1 nm to 200 nm.

17. The method of claim 15 , wherein the sidewall insulating layer includes more than one layers made of different materials.

18. A method for manufacturing a semiconductor structure, 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 spacers on sidewalls of the dummy gate structure;

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

forming interlayer dielectric layers on the second dielectric layer;

removing the dummy gate structure to form a trench between the 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, after the gate structure is formed, the first dielectric layer is disposed between the spacers and the isolation structure, the spacers and the first dielectric layer are made of different materials, and the spacers are in direct contact with the gate structure.

19. The method of claim 18 , wherein the gate structure is in direct contact with the first dielectric layer and the spacers and the second dielectric layer is not disposed between the spacers and the isolation structure.