Fin end isolation structure for semiconductor devices

1. A semiconductor structure, comprising:

a substrate;

first and second semiconductor fins extending from the substrate, wherein the first and the second semiconductor fins are lengthwise aligned along a first direction;

an isolation structure over the substrate and adjacent to sidewalls of the first and the second semiconductor fins;

first and second gate structures that are oriented lengthwise along a second direction generally perpendicular to the first direction, wherein the first and the second gate structures are disposed over the isolation structure, the first gate structure is disposed over the first semiconductor fin, and the second gate structure is disposed over the second semiconductor fin; and

a spacer layer that is disposed on a sidewall of the first gate structure and on a sidewall of the second gate structure and extends continuously through a trench between an end of the first semiconductor fin and an end of the second semiconductor fin.

2. The semiconductor structure of claim 1 , wherein the trench is substantially rectangular from a top view, and the end of the first semiconductor fin and the end of the second semiconductor fin form at least portions of two opposing sidewalls of the trench.

3. The semiconductor structure of claim 2 , wherein the spacer layer is disposed over the two opposing sidewalls of the trench and at bottom of the trench.

4. The semiconductor structure of claim 2 , wherein sidewalls of the isolation structure form at least portions of other two opposing sidewalls of the trench.

5. The semiconductor structure of claim 1 , wherein a top surface of a portion of the spacer layer within the trench is below a top surface of the isolation structure.

6. The semiconductor structure of claim 1 , wherein a portion of the spacer layer within the trench extends below a top surface of the substrate.

7. The semiconductor structure of claim 1 , wherein a side of the first gate structure is substantially aligned with the end of the first semiconductor fin from a top view.

8. The semiconductor structure of claim 7 , wherein a side of the second gate structure is substantially aligned with the end of the second semiconductor fin from a top view.

9. The semiconductor structure of claim 1 , further comprising:

an inter-layer dielectric layer that is disposed over the first and the second gate structures and fills in a portion of the trench.

10. The semiconductor structure of claim 1 , further comprising:

third and fourth gate structures that are parallel to each other and oriented lengthwise along the second direction, wherein the third and the fourth gate structures are disposed over the isolation structure, the third gate structure is disposed over a channel region of the first semiconductor fin, and the fourth gate structure is disposed over a channel region of the second semiconductor fin.

11. The semiconductor structure of claim 10 , further comprising:

a third semiconductor fin extending from the substrate, wherein the third semiconductor fin is lengthwise parallel to the first and the second semiconductor fins, wherein a side of the third gate structure is substantially aligned with an end of the third semiconductor fin and a side of the fourth gate structure is substantially aligned with another end of the third semiconductor fin from a top view.

12. A semiconductor structure, comprising:

a substrate;

first and second semiconductor fins extending from the substrate, wherein the first and the second semiconductor fins are lengthwise aligned along a first direction, and a first end of the first semiconductor fin faces a second end of the second semiconductor fin;

a first isolation structure over the substrate and adjacent to sidewalls of the first and the second semiconductor fins;

first and second gate structures that are oriented lengthwise along a second direction generally perpendicular to the first direction, wherein the first and the second gate structures are disposed over the first isolation structure, the first gate structure is disposed over the first semiconductor fin, and the second gate structure is disposed over the second semiconductor fin; and

a second isolation structure extending from the first end of the first semiconductor fin to the second end of the second semiconductor fin, wherein the first and the second isolation structures include different dielectric materials.

13. The semiconductor structure of claim 12 , wherein a side of the first gate structure is substantially aligned with the first end of the first semiconductor fin and a side of the second gate structure is substantially aligned with the second end of the second semiconductor fin from a top view.

14. The semiconductor structure of claim 12 , wherein the second isolation structure includes a portion of a spacer layer that extends continuously through a trench between the first end of the first semiconductor fin and the second end of the second semiconductor fin, wherein the spacer layer is further disposed over a sidewall of the first gate structure and over a sidewall of the second gate structure.

15. The semiconductor structure of claim 12 , wherein the second isolation structure includes a portion of an inter-layer dielectric layer, wherein the inter-layer dielectric layer is further disposed over the first and the second gate structures.

16. The semiconductor structure of claim 12 , further comprising a spacer layer disposed over a sidewall of the first gate structure and over a sidewall of the second gate structure, wherein the first end of the first semiconductor fin and the second end of the second semiconductor fin are directly under the spacer layer.

17. A semiconductor structure, comprising:

a substrate;

first and second semiconductor fins over the substrate and extending lengthwise aligned along a first direction from a top view;

an isolation structure over the substrate and adjacent to the first and the second semiconductor fins;

first and second gate structures extending lengthwise generally along a second direction perpendicular to the first direction, wherein the first gate structure is disposed over both the isolation structure and the first semiconductor fin, and the second gate structure is disposed over both the isolation structure and the second semiconductor fin; and

a spacer layer disposed on a sidewall of the first gate structure, a sidewall of the second gate structure, a vertical end of the first semiconductor fin, a vertical end of the second semiconductor fin, and a top surface of the substrate.

18. The semiconductor structure of claim 17 , wherein the spacer layer is also disposed on two vertical surfaces of the isolation structure.

19. The semiconductor structure of claim 17 , further comprising:

an inter-layer dielectric layer, wherein a portion of the inter-layer dielectric layer is in direct contact with the spacer layer and extends below a top surface of the first semiconductor fin.

20. The semiconductor structure of claim 17 , wherein a bottom surface of the spacer layer is below a topmost surface of the substrate.