Semiconductor device structure

1. A semiconductor structure, comprising:

a substrate comprising a p-type well and an n-type well;

a first base portion over the p-type well;

a second base portion over the n-type well;

a first plurality of channel members over the first base portion, the first plurality of channel members being stacked one over another;

a second plurality of channel members over the second base portion, the second plurality of channel members being stacked one over another;

an isolation feature disposed between the first base portion and the second base portion; and

a deep isolation structure in the substrate disposed below the isolation feature.

2. The semiconductor structure of claim 1 , wherein the isolation feature and the deep isolation structure extend through a junction between the p-type well and the n-type well.

3. The semiconductor structure of claim 1 , wherein the deep isolation structure comprises silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride, or silicon oxycarbonitride.

4. The semiconductor structure of claim 1 , wherein a shape of the isolation feature is different from a shape of the deep isolation structure.

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

a first gate structure wrapping around each of the first plurality of channel members;

a second gate structure wrapping around each of the second plurality of channel members; and

a first dielectric fin disposed between the first gate structure and the second gate structure.

6. The semiconductor structure of claim 5 , wherein the first dielectric fin is disposed on the isolation feature.

7. The semiconductor structure of claim 5 , wherein a first portion of the first gate structure extends between the first dielectric fin and the first plurality of channel members.

8. The semiconductor structure of claim 7 , further comprising:

a second dielectric fin in contact with sidewalls of the first plurality of channel members.

9. The semiconductor structure of claim 5 , wherein a second portion of the first gate structure extends between the first dielectric fin and the first base portion.

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

a second dielectric fin in contact with the first base portion.

11. A semiconductor structure, comprising:

a substrate comprising a p-type well and an n-type well;

a first semiconductor base portion over the p-type well;

a second semiconductor base portion over the n-type well;

a first n-type epitaxial feature over the first semiconductor base portion;

a first p-type epitaxial feature over the second semiconductor base portion;

a first isolation feature disposed between the first semiconductor base portion and the second semiconductor base portion; and

a deep isolation structure in the substrate disposed directly below the first isolation feature.

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

a first dielectric fin disposed on the first isolation feature,

wherein the first dielectric fin is sandwiched between the first n-type epitaxial feature and the first p-type epitaxial feature,

wherein a width of the first dielectric fin is smaller than a width of the first isolation feature.

13. The semiconductor structure of claim 11 , wherein a shape of the first isolation feature is different from a shape of the deep isolation structure.

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

a third semiconductor base portion over the p-type well;

a second n-type epitaxial feature over the third semiconductor base portion; and

a second isolation feature disposed between the first semiconductor base portion and the third semiconductor base portion,

wherein a width of the first isolation feature is greater than a width of the second isolation feature.

15. The semiconductor structure of claim 14 , further comprising:

a second dielectric fin disposed over the second isolation feature,

wherein the second dielectric fin is sandwiched between the first n-type epitaxial feature and the second n-type epitaxial feature,

wherein a width of the second dielectric fin is substantially identical to a width of the second isolation feature.

16. A semiconductor structure, comprising:

a substrate comprising a p-type well and an n-type well;

a first active region over the p-type well;

a second active region over the n-type well;

a first gate structure disposed over the first active region;

a second gate structure disposed over the second active region;

a junction isolation feature disposed between the p-type well and the n-type well along a direction; and

a deep isolation feature disposed below and extending from the junction isolation feature, wherein the deep isolation feature is wider than the junction isolation feature along the direction,

wherein a portion of the first gate structure and a portion of the second gate structure are disposed over a top surface of the junction isolation feature.

17. The semiconductor structure of claim 16 , further comprising:

a dielectric fin disposed on the junction isolation feature, wherein the junction isolation feature is wider than the dielectric fin along the direction.

18. The semiconductor structure of claim 16 , further comprising:

a first isolation feature disposed within the p-type well; and

a second isolation feature disposed within the n-type well,

wherein the junction isolation feature is wider than the first isolation feature and the second isolation feature along the direction.

19. The semiconductor structure of claim 16 , wherein a height of the deep isolation feature is greater than a height of the junction isolation feature.

20. The semiconductor structure of claim 18 , wherein the junction isolation feature, the deep isolation feature, the first isolation feature, and the second isolation feature comprise silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride, or silicon oxycarbonitride.