Semiconductor device structure and method for forming the same

1. A semiconductor device structure, comprising:

an isolation structure formed over a substrate;

a first stacked structure and a second stacked structure extending above the isolation structure, wherein the first stacked structure comprises a plurality of first nanostructures stacked in a vertical direction, and the second stacked structure comprises a plurality of second nanostructures stacked in the vertical direction;

a first dummy fin structure formed over the isolation structure, wherein the first dummy fin structure is between the first fin structure and the second fin structure; and

a capping layer formed over the first dummy fin structure, wherein a top surface of the capping layer is higher than a top surface of the first stacked structure and a top surface of the second stacked structure.

2. The semiconductor device structure as claimed in claim 1 , wherein the isolation structure has a first width, the first dummy fin structure has a second width, and the second width is smaller than the first width.

3. The semiconductor device structure as claimed in claim 2 , wherein the second width of the first dummy fin structure is in a range from about 5 nm to about 20 nm.

4. The semiconductor device structure as claimed in claim 1 , further comprising:

a second dummy fin structure adjacent to the second fin structure, wherein the second dummy fin structure has a recessed portion, and a dielectric layer is formed over the recessed portion.

5. The semiconductor device structure as claimed in claim 4 , wherein a width of the dielectric layer is greater than a width of the second dummy fin structure.

6. The semiconductor device structure as claimed in claim 1 , further comprising:

a first gate structure formed over the first stacked structure; and

a second gate structure formed over the second stacked structure, wherein the top surface of the capping layer is higher than a top surface of the first gate structure and a top surface of the second gate structure.

7. The semiconductor device structure as claimed in claim 1 , wherein a top surface of the first dummy fin structure is higher than a top surface of a topmost of the first nanostructures.

8. The semiconductor device structure as claimed in claim 1 , wherein the first dummy fin structure is made of low-k dielectric material, and the capping layer is made of high-k dielectric material.

9. The semiconductor device structure as claimed in claim 1 , further comprising:

an inner spacer layer formed on a sidewall surface of the first stacked structure and a sidewall surface of the second stacked structure.

10. A semiconductor device structure, comprising:

an isolation structure formed over a substrate;

a first stacked structure, a second stacked structure and a third stacked structure extending above the isolation structure, wherein each of the first stacked structure, the second stacked structure, and the third stacked structure comprises a plurality of nanostructures stacked in a vertical direction;

a first dummy fin structure formed over the isolation structure, wherein the first dummy fin structure is between the first stacked structure and the second stacked structure; and

a second dummy fin structure formed between the second stacked structure and the third stacked structure, wherein the second dummy fin structure has a U-shaped structure.

11. The semiconductor device structure as claimed in claim 10 , further comprising:

a capping layer formed over the first dummy fin structure, wherein the first dummy fin structure and the capping layer are made of different materials.

12. The semiconductor device structure as claimed in claim 11 , further comprising:

a first gate structure formed on the first stacked structure; and

a second gate structure formed on the second stacked structure and the third stacked structure, wherein the first gate structure and the second gate structure are separated by the first dummy fin structure and the capping layer.

13. The semiconductor device structure as claimed in claim 10 , further comprising:

an inner spacer layer formed on a sidewall surface of the first stacked structure, and a sidewall surface of the second stacked structure.

14. The semiconductor device structure as claimed in claim 10 , further comprising:

a filling layer formed over the second dummy fin structure, wherein a top surface of the filling layer is leveled with a top surface of the second dummy fin structure.

15. The semiconductor device structure as claimed in claim 10 , wherein the isolation structure has a first width, the second dummy fin structure has a second width, and the second width is smaller than the first width.

16. The semiconductor device structure as claimed in claim 10 , wherein the isolation structure comprises a first isolation layer directly below the first dummy fin structure and a second isolation layer directly below the second dummy fin structure, wherein a width of the first isolation layer is smaller than a width of the second isolation layer.

17. A method for forming a semiconductor device structure, comprising:

forming a first stacked structure and a second stacked structure extending above an isolation structure, wherein each of the first stacked structure and the second stacked structure comprises a plurality of first semiconductor layers and a plurality of second semiconductor layers alternately stacked in a vertical direction;

forming a first dummy fin structure and a second dummy fin structure over the isolation structure, wherein the first dummy fin structure is between the first fin structure and the second fin structure, the second fin structure is between the first dummy fin structure and the second dummy fin structure, and the second dummy fin structure has a U-shaped structure;

forming a first capping layer over the first dummy fin structure; and

forming a second capping layer over the second dummy fin structure, wherein a width of the first capping layer is smaller than a width of the second capping layer.

18. The method for forming the semiconductor device structure as claimed in claim 17 , further comprising:

forming a dummy gate structure over the first capping layer, the second capping layer, the first stacked structure, and the second stacked structure;

forming a dielectric layer surrounding the dummy gate structure;

removing the dummy gate structure to form a trench in the dielectric layer;

removing a portion of the first semiconductor layers in the first stacked structure to form a first gap and removing a portion of the first semiconductor layers in the second stacked structure to form a second gap; and

forming a first gate structure in the first gap and forming a second gate structure in the second gap, wherein a top surface of the first capping layer is higher than a top surface of the first gate structure.

19. The method for forming the semiconductor device structure as claimed in claim 17 , further comprising:

removing a portion of the first stacked structure and a portion of the second stacked structure to form a first source/drain (S/D) recess and a second S/D recess, respectively;

forming a first source/drain (S/D) structure in the first S/D recess and forming a second S/D structure in the second S/D recess.

20. The method for forming the semiconductor device structure as claimed in claim 19 , further comprising:

forming a liner on a sidewall surface of the first fin structure and a sidewall surface of the second fin structure before forming the first dummy fin structure and the second dummy fin structure;

removing a portion of the liner to form a cavity; and

forming an inner spacer layer in the cavity before forming the first S/D structure in the first S/D recess and forming the second S/D structure in the second S/D recess, wherein the inner spacer layer is in direct contact with the first stacked structure and the first capping layer.