Semiconductor devices having gate structures with slanted sidewalls

1. A structure comprising:

a nano-structure;

an epitaxial source/drain region adjacent the nano-structure;

a gate dielectric wrapped around the nano-structure;

a gate electrode over the gate dielectric, the gate electrode having an upper portion and a lower portion, a first width of the upper portion increasing continually in a first direction extending away from a top surface of the nano-structure, a second width of the lower portion being constant along the first direction; and

a gate spacer between the gate dielectric and the epitaxial source/drain region, the gate spacer having a first sidewall facing the epitaxial source/drain region and a second sidewall facing the gate dielectric, the first sidewall and the second sidewall of the gate spacer meeting at an apex.

2. The structure of claim 1 , wherein the gate electrode comprises an interior corner at interfaces of the upper portion and the lower portion, sidewalls of the gate electrode forming an angle at the interior corner, the angle being in a range of 183 degrees to 230 degrees.

3. The structure of claim 1 , wherein the gate spacer has an upper portion and a lower portion, a third width of the upper portion decreasing continually in the first direction, a fourth width of the lower portion being constant along the first direction.

4. The structure of claim 1 further comprising:

a gate mask over the gate electrode and the gate dielectric, the gate mask having slanted sidewalls; and

a gate contact extending through the gate mask to contact the gate electrode.

5. The structure of claim 1 , wherein the gate spacer comprises silicon oxycarbonitride having a first concentration of oxygen in an upper portion of the gate spacer and a second concentration of oxygen in a lower portion of the gate spacer, the second concentration being less than the first concentration.

6. The structure of claim 1 , wherein the gate spacer comprises silicon oxycarbonitride having a first concentration of nitrogen in an upper portion of the gate spacer and a second concentration of nitrogen in a lower portion of the gate spacer, the second concentration being less than the first concentration.

7. A structure comprising:

a nano-structure;

a gate structure wrapped around the nano-structure;

a first pair of gate spacers adjacent the gate structure, the first pair of gate spacers being separated by a first distance at a lower portion of the gate structure, the first pair of gate spacers being separated by a second distance at an upper portion of the gate structure, the second distance being greater than the first distance;

a gate mask over the gate structure, the gate mask having slanted sidewalls; and

a gate contact extending through the gate mask to contact the gate structure.

8. The structure of claim 7 , wherein a ratio of the second distance to the first distance is in a range of 1.1 to 11.

9. The structure of claim 7 , wherein the lower portion of the gate structure has parallel sidewalls, and the upper portion of the gate structure has slanted sidewalls.

10. The structure of claim 9 , wherein the slanted sidewalls of the gate mask are aligned with the slanted sidewalls of the upper portion of the gate structure.

11. The structure of claim 7 , wherein upper portions of the first pair of gate spacers comprise SiO x N y C 1-x-y where x is greater than y, and wherein lower portions of the first pair of gate spacers comprise SiO x N y C 1-x-y where x is less than y.

12. A structure comprising:

a gate structure over a channel region, an upper portion of the gate structure having slanted sidewalls, a lower portion of the gate structure having parallel sidewalls;

a gate mask over the gate structure, the gate mask having slanted sidewalls, the slanted sidewalls of the gate mask aligned with the slanted sidewalls of the upper portion of the gate structure;

a first pair of gate spacers contacting the parallel sidewalls of the lower portion of the gate structure and the slanted sidewalls of the upper portion of the gate structure; and

a second pair of gate spacers contacting outer sidewalls of the first pair of gate spacers, the slanted sidewalls of the upper portion of the gate structure, and the slanted sidewalls of the gate mask.

13. The structure of claim 12 further comprising:

a gate contact extending through the gate mask to contact the gate structure.

14. The structure of claim 12 , wherein upper portions of the first pair of gate spacers have a greater concentration of oxygen than lower portions of the first pair of gate spacers.

15. The structure of claim 12 , wherein upper portions of the first pair of gate spacers have a greater concentration of nitrogen than lower portions of the first pair of gate spacers.

16. The structure of claim 12 , wherein the parallel sidewalls of the lower portion of the gate structure form angles with the slanted sidewalls of the upper portion of the gate structure, the angles being in a range of 183 degrees to 230 degrees.

17. The structure of claim 12 , wherein the outer sidewalls of the first pair of gate spacers and inner sidewalls of the first pair of gate spacers meet at an apex.

18. The structure of claim 17 , wherein the outer sidewalls of the first pair of gate spacers form angles with the inner sidewalls of the first pair of gate spacers, the angles being in a range of 3 degrees to 50 degrees.

19. The structure of claim 12 , wherein a top surface of the gate mask is coplanar with top surfaces of the second pair of gate spacers.

20. The structure of claim 12 , wherein the first pair of gate spacers are between the channel region and the second pair of gate spacers.