Transistor device having a comb-shaped channel region to increase the effective gate width

1. A method of forming a comb-shaped transistor device, comprising:

forming a stack of alternating sacrificial spacer segments and channel segments on a substrate;

forming channel sidewalls on opposite sides of the stack of alternating sacrificial spacer segments and channel segments;

dividing the stack of alternating sacrificial spacer segments and channel segments into alternating sacrificial spacer slabs and channel slabs, wherein the channel slabs and channel sidewalls form a pair of comb-like structures;

trimming the sacrificial spacer slabs and channel slabs to form a nanosheet column of sacrificial plates and channel plates; and

forming source/drains on opposite sides of the sacrificial plates and channel plates.

2. The method of claim 1 , further comprising forming a dummy gate structure across the pair of comb-like structures, and using the dummy gate structure as a mask for trimming the sacrificial spacer slabs and channel slabs.

3. The method of claim 2 , further comprising removing a portion of the sacrificial plates from opposite sides to form recesses, and forming inner spacers in the recesses.

4. The method of claim 3 , further comprising removing a portion of the dummy gate structure to expose the sacrificial plates, and removing the sacrificial plates to expose portions of the channel slabs.

5. The method of claim 4 , further comprising forming a gate-all-around structure of the exposed portions of the channel slabs.

6. The method of claim 5 , wherein the channel sidewall and channel plates form a comb-like channel structure for a field effect transistor device.

7. The method of claim 1 , wherein the channel sidewalls are formed by lateral epitaxial growth.

8. The method of claim 7 , wherein the sacrificial spacer segments are silicon-germanium (SiGe) and the channel segments are silicon (Si).

9. The method of claim 8 , wherein the sacrificial spacer segments have a thickness in a range of about 6 nanometers (nm) to about 30 nm, and the channel segments have a thickness in a range of about 4 nanometers (nm) to about 12 nm.

10. A method of forming a comb-shaped transistor device, comprising:

forming a stack of alternating sacrificial spacer segments and channel segments on a substrate;

forming channel sidewalls on opposite sides of the stack of alternating sacrificial spacer segments and channel segments;

forming a pair of partition templates on the exposed surface of a topmost sacrificial spacer segment, wherein a center portion of the topmost sacrificial spacer segment is exposed between the pair of partition templates;

dividing the stack of alternating sacrificial spacer segments and channel segments into alternating sacrificial spacer slabs and channel slabs, wherein the channel slabs and channel sidewalls form an adjacent pair of comb-like structures;

forming a dummy gate structure across the pair of comb-like structures;

trimming the sacrificial spacer slabs and channel slabs using the dummy gate structure as a mask to form a nanosheet column of sacrificial plates and channel plates; and

forming source/drains on opposite sides of the sacrificial plates and channel plates.

11. The method of claim 10 , wherein the sacrificial spacer segments are silicon-germanium (SiGe) and the channel segments are silicon (Si).

12. The method of claim 11 , further comprising removing a portion of the sacrificial plates from opposite sides to form recesses, and forming inner spacers in the recesses.

13. The method of claim 10 , wherein the channel sidewalls have a thickness about equal to the thickness of the channel segments.

14. The method of claim 13 , wherein the channel segments have a thickness in a range of about 4 nanometers (nm) to about 12 nm.

15. The method of claim 14 , wherein the source/drains on the adjacent pair of comb-like structures form merged source/drains.