Multi-gate transistor structure

1. A semiconductor device, comprising:

a first channel member comprising a first channel portion and a first connection portion;

a second channel member comprising a second channel portion and a second connection portion;

a gate structure disposed around the first channel portion and the second channel portion, the gate structure comprising a gate dielectric layer and a gate electrode; and

an inner spacer feature disposed between the first connection portion and the second connection portion,

wherein the gate dielectric layer extends partially between the inner spacer feature and the first connection portion and between the inner spacer feature and the second connection portion,

wherein the gate electrode is absent from between the inner spacer feature and the first connection portion and between the inner spacer feature and the second connection portion.

2. The semiconductor device of claim 1 , wherein a thickness of the first channel portion is substantially equal to a thickness of the first connection portion.

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

a source/drain feature, wherein the first connection portion and the second connection portion are coupled to the source/drain feature.

4. The semiconductor device of claim 3 ,

wherein the inner spacer feature comprises a first inner spacer layer adjacent the gate dielectric layer and a second inner spacer layer adjacent the source/drain feature,

wherein a dielectric constant of the first inner spacer layer is greater than a dielectric constant of the second inner spacer layer.

5. The semiconductor device of claim 1 ,

wherein the first channel member and the second channel member extend lengthwise along a first direction,

wherein the second channel member is disposed over the first channel member,

wherein the gate electrode comprises a topmost portion disposed over the second channel portion and an inter-member portion disposed between the first channel portion and the second channel portion,

wherein a length of the topmost portion along the first direction is greater than a length of the inter-member portion along the first direction.

6. The semiconductor device of claim 5 , further comprising:

a gate spacer layer disposed along a sidewall of the topmost portion,

wherein the second connection portion is disposed between the inner spacer feature and the gate spacer layer,

wherein a width of the gate spacer layer along the first direction is smaller than a width of the inner spacer feature along the first direction.

7. The semiconductor device of claim 5 ,

wherein the gate structure extends lengthwise along a second direction perpendicular to the first direction,

wherein, when viewed along the second direction, the inner spacer feature includes a C-shape.

8. The semiconductor device of claim 7 ,

wherein the gate structure extends lengthwise along a second direction perpendicular to the first direction,

wherein, when viewed along the second direction, the inner spacer feature extends below the topmost portion of the gate electrode.

9. A structure, comprising:

a gate structure extending lengthwise along a first direction;

an isolation gate structure extending parallel to the gate structure;

a source/drain feature disposed between the gate structure and the isolation gate structure along a second direction perpendicular to the first direction; and

a plurality of first semiconductor features sandwiched between the isolation gate structure and the source/drain feature along the second direction, the plurality of first semiconductor features being stacked one over another along a third direction perpendicular to the first direction and the second direction,

wherein the plurality of first semiconductor features are interleaved by a plurality of inner spacer features.

10. The structure of claim 9 , wherein, when viewed along the first direction, each of the plurality of inner spacer features comprises a C-shape.

11. The structure of claim 9 , wherein the isolation gate structure is insulative and comprises silicon nitride or a metal oxide.

12. The structure of claim 9 , wherein the plurality of inner spacer features comprise silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, or silicon oxycarbonitride.

13. The structure of claim 9 , further comprising a spacer layer disposed over a topmost first semiconductor feature of the plurality of first semiconductor features,

wherein the spacer layer extends along a sidewall of the isolation gate structure.

14. The structure of claim 9 ,

wherein the plurality of first semiconductor features are further interleaved by a plurality of second semiconductor features along the third direction,

wherein the plurality of first semiconductor features comprise silicon and the plurality of second semiconductor features comprise silicon germanium.

15. The structure of claim 14 , wherein each of the plurality of inner spacer features extends into one of the plurality of second semiconductor features along the second direction.

16. A semiconductor device, comprising:

a first source/drain feature and a second source/drain feature;

a plurality of channel members stacked vertically and extending between the first source/drain feature and the second source/drain feature along a direction;

a plurality of inner spacer features in contact with the first source/drain feature and interleaving the plurality of channel members; and

a gate structure disposed over and wrapping around the plurality of channel members,

wherein the gate structure comprises a gate dielectric layer in contact with the plurality of inner spacer features and a gate electrode spaced apart from the plurality of inner spacer features,

wherein the gate dielectric layer partially extends between the plurality of channel members and the plurality of inner spacer features.

17. The semiconductor device of claim 16 ,

wherein the gate electrode comprises a topmost portion above the plurality of channel members and an inter-member portion between two of the plurality of channel members,

wherein a width of the topmost portion along the direction is greater than a width of the inter-member portion along the direction.

18. The semiconductor device of claim 17 ,

wherein a width of the gate dielectric layer along the direction is greater than the width of the topmost portion along the direction.

19. The semiconductor device of claim 16 ,

wherein each of the plurality of inner spacer features comprises a first inner spacer layer adjacent the gate dielectric layer and a second inner spacer layer adjacent the first source/drain feature,

wherein a dielectric constant of the first inner spacer layer is greater than a dielectric constant of the second inner spacer layer.

20. The semiconductor device of claim 19 , wherein a nitrogen content of the first inner spacer layer is greater than a nitrogen content of the second inner spacer layer.