Semiconductor device and method

1. A semiconductor device comprising:

a semiconductor substrate;

a channel region over the semiconductor substrate, the channel region comprising a first semiconductor layer;

a gate stack over the channel region, the gate stack comprising a gate electrode and a gate dielectric;

a first epitaxial source/drain region adjacent the channel region; and

a first inner spacer between the first semiconductor layer and the first epitaxial source/drain region, the first inner spacer comprising SiOCN, the first inner spacer having an oxidized layer to a depth in a range of 1 nm to 5 nm, the oxidized layer having a gradient of atomic percentage of oxygen from 30% to 60% measured from a first sidewall of the first inner spacer contacting the epitaxial source/drain region into the first inner spacer.

2. The semiconductor device of claim 1 , wherein the channel region further comprises a multi-layer stack of semiconductor layers and wherein portions of the gate electrode are between semiconductor layers of the multi-layer stack.

3. The semiconductor device of claim 1 , wherein the first inner spacer has dishing to a distance of less than 0.5 nm.

4. The semiconductor device of claim 1 , wherein the first inner spacer has a second sidewall contacting the gate dielectric, and a maximum horizontal distance measured between the second sidewall and a vertical line through top and bottom vertices of the second sidewall is in a range of 1 nm to 2 nm.

5. The semiconductor device of claim 1 , wherein the first inner spacer has a density in a range of 2.5 g/cm 3 to 2.9 g/cm 3 .

6. The semiconductor device of claim 1 , wherein the first inner spacer comprises a gradient of atomic percentage of carbon from 7% to 9% measured from the first sidewall of the first inner spacer contacting the epitaxial source/drain region into the first inner spacer.

7. The semiconductor device of claim 1 , wherein the first inner spacer comprises a gradient of atomic percentage of nitrogen from 25% to 20% measured from the first sidewall of the first inner spacer contacting the epitaxial source/drain region into the first inner spacer.

8. The semiconductor device of claim 1 , wherein the first inner spacer comprises a gradient of atomic percentage of silicon from 35% to 45% measured from the first sidewall of the first inner spacer contacting the epitaxial source/drain region into the first inner spacer.

9. A method comprising:

forming a multi-layer stack on a semiconductor substrate, the multi-layer stack comprising alternating first layers and second layers, the first layers being a first semiconductor material, the second layers being a second semiconductor material;

forming a first recess through the multi-layer stack;

laterally recessing sidewalls of the second layers of the multi-layer stack, the sidewalls being adjacent to the first recess;

forming an inner spacer layer over the multi-layer stack, the inner spacer layer having seams;

performing an anneal treatment on the inner spacer layer, the anneal treatment comprising a wet anneal and a dry anneal, the anneal treatment closing the seams of the inner spacer layer;

removing an outer portion of the inner spacer layer to form inner spacers adjacent to the recessed second layers of the multi-layer stack; and removing the second layers of the multi-layer stack.

10. The method of claim 9 , wherein the seams of the inner spacer layer close while the wet anneal is performed.

11. The method of claim 10 , wherein the wet anneal converts Si—NH—Si bonds in the inner spacer layer to Si—OH—Si bonds.

12. The method of claim 11 , wherein the dry anneal converts the Si—OH—Si bonds in the inner spacer layer to Si—O—Si bonds.

13. A method of forming a semiconductor device, the method comprising:

depositing alternating layers of a first semiconductor material and a second semiconductor material on a semiconductor substrate;

forming a first dummy gate and a second dummy gate on the alternating layers, the first dummy gate being in a first channel region, the second dummy gate being in a second channel region;

etching a first recess through the alternating layers using the first dummy gate and the second dummy gate as masks;

removing outer portions of the alternating layers of the first semiconductor material, the removing the outer portions forming a plurality of second recesses;

depositing an inner spacer layer over the alternating layers of the first semiconductor material and the second semiconductor material;

performing a steam anneal on the inner spacer layer;

performing a dry anneal on the inner spacer layer;

etching the inner spacer layer to form respective inner spacers in the plurality of second recesses; and

removing the alternating layers of the first semiconductor material.

14. The method of claim 13 , wherein depositing the inner spacer layer comprises forming a SiOCN film using H 2 SiCl 2 , C 3 H 6 , O 2 , and NH 3 as precursors.

15. The method of claim 13 , wherein the steam anneal is an H 2 O anneal performed in a furnace at a temperature in a range of 200° C. to 600° C.

16. The method of claim 13 , wherein the dry anneal is an N 2 anneal performed in a furnace at a temperature in a range of 600° C. to 700° C.

17. The method of claim 13 , wherein the inner spacer layer expands by 10% after the performing the steam anneal.

18. The method of claim 13 , wherein the inner spacer layer comprises a contact angle in a range of 25° to 30° before performing the steam anneal.

19. The method of claim 13 , wherein the inner spacer layer comprises a contact angle in a range of 33° to 40° after performing the steam anneal.

20. The method of claim 13 , wherein the etching the inner spacer layer comprises a wet etch process comprising HF, H 2 O 2 , H 2 O, HClNH 3 , or H 2 SO 4 .