Metal gate structure cutting process

1. A semiconductor device, comprising:

a first gate structure and a second gate structure disposed in an interlayer dielectric (ILD) layer disposed on a substrate, wherein each of the first gate structure and the second gate structure comprises a gate dielectric and a gate electrode;

an isolation structure disposed between the first gate structure and the second gate structure, wherein the ILD layer circumscribes a perimeter of the isolation structure; and

a dielectric structure disposed between the ILD layer and the isolation structure, wherein a bottom surface of the isolation structure is closer to the substrate than a bottom surface of the dielectric structure, wherein the isolation structure directly contacts the gate electrode of the first gate structure.

2. The semiconductor device of claim 1 , wherein the gate electrode of each of the first gate structure and the second gate structure comprises a work function layer.

3. The semiconductor device of claim 1 , wherein the dielectric structure includes a first material different from a second material of the isolation structure.

4. The semiconductor device of claim 3 , wherein the first material of the dielectric structure is different from a third material of the ILD layer.

5. The semiconductor device of claim 1 , wherein the dielectric structure is a conformal liner layer interfaced between the isolation structure and the ILD layer.

6. The semiconductor device of claim 1 , wherein the isolation structure has a top surface and a bottom surface, wherein the bottom surface of the isolation structure has step heights, creating a varying depth across a body of the isolation structure.

7. The semiconductor device of claim 1 , further comprising:

an etch stop layer disposed between the isolation structure and ILD layer.

8. The semiconductor device of claim 1 , wherein the first gate structure and the second gate structure on the substrate have mismatched dimensions.

9. A semiconductor device, comprising:

a first gate structure and a second gate structure;

a first isolation structure interposed between an end of the first gate structure and an end of the second gate structure, wherein the first isolation structure extends over a shallow trench isolation interposed between two fins, wherein the first isolation structure has a first thickness at a first location and has a second thickness at a second location, wherein the first thickness is less than the second thickness;

a second isolation structure along opposing sidewalls of the first gate structure and the second gate structure; and

a third isolation structure interposed between the first isolation structure and the second isolation structure, wherein the third isolation structure does not separate the first isolation structure from the first gate structure.

10. The semiconductor device of claim 9 , wherein the second isolation structure does not extend between the first isolation structure and the first gate structure, and wherein the second isolation structure does not extend between the first isolation structure and the second gate structure.

11. The semiconductor device of claim 9 , wherein the first isolation structure extends lower than the third isolation structure.

12. The semiconductor device of claim 11 , wherein the first isolation structure extends lower than the second isolation structure.

13. The semiconductor device of claim 12 , wherein the first isolation structure contacts the second isolation structure below the third isolation structure.

14. The semiconductor device of claim 9 , wherein the first isolation structure contacts the first gate structure and the second gate structure.

15. A semiconductor device, comprising:

a first transistor including a first source/drain region, a second source/drain region, a first gate structure extending along sidewalls of a first fin, the first gate structure extending over a first shallow trench isolation;

a second transistor including a third source/drain region, a fourth source/drain region, a second gate structure extending along sidewalls of a second fin, the second gate structure extending over the first shallow trench isolation, the first gate structure and the second gate structure being aligned along a first longitudinal axis;

a first isolation structure contacting the first gate structure and the second gate structure;

a second isolation structure over the first source/drain region and the third source/drain region; and

a third isolation structure interposed between the first isolation structure and the first source/drain region and between the first isolation structure and the third source/drain region, the third isolation structure extending along a sidewall of the first isolation structure, the sidewalls of the first isolation structure being parallel to current flow between the first source/drain region and the second source/drain region.

16. The semiconductor device of claim 15 , wherein a bottom surface of the first isolation structure contacts the third isolation structure.

17. The semiconductor device of claim 15 , wherein a bottom surface of the first isolation structure contacts the first shallow trench isolation.

18. The semiconductor device of claim 15 , wherein at least a portion of the third isolation structure is interposed between a bottom surface of the first isolation structure and the first shallow trench isolation.

19. The semiconductor device of claim 15 , wherein a bottom surface of the first isolation structure comprises a plurality of projections.

20. The semiconductor device of claim 9 , further comprising an isolation region, wherein the first gate structure and the second gate structure extends over the isolation region, wherein the first isolation structure directly contacts the isolation region.