FinFET gate formation using reverse trim and oxide polish

1. A method of forming a gate electrode for a fin field effect transistor (FinFET), comprising:

forming a fin on a substrate;

forming an oxide layer over the fin;

forming a trench in the oxide layer, the trench crossing over the fin; and

filling the trench with a material to form a gate electrode.

2. The method of claim 1 , further comprising:

forming a layer of anti-reflective coating (ARC) on the oxide layer.

3. The method of claim 2 , further comprising:

depositing and patterning a layer of photo-resist material over the anti-reflective coating.

4. The method of claim 3 , further comprising:

etching away at least a portion of the oxide layer to form a protrusion above the fin.

5. The method of claim 4 , further comprising:

forming a second nitride layer on the oxide layer.

6. The method of claim 5 , further comprising:

polishing the nitride layer to remove at least a portion of the protrusion and expose a top surface of the protrusion.

7. The method of claim 6 , further comprising:

etching the protrusion and the oxide layer to form the trench.

8. The method of claim 7 , further comprising:

removing the second nitride layer.

9. The method of claim 8 , further comprising:

forming a dielectric layer over the fin within the trench.

10. The method of claim 9 , wherein filling the trench with the material further comprises:

depositing at least one of a polysilicon and a metal material to form the gate electrode.

11. The method of claim 10 , further comprising;

planarizing the deposited material.

12. The method of claim 1 , further comprising:

forming a first nitride layer over the fin before forming the oxide layer over the fin.

13. A method of forming a gate for a fin field effect transistor (FinFET), comprising:

forming an oxide layer over a fin;

etching away at least a portion of the oxide layer to form a protrusion above the fin;

forming a nitride layer over the oxide layer and the protrusion;

polishing the nitride layer and the protrusion to expose a top surface of the protrusion;

etching the protrusion and the oxide layer to form a trench that crosses over the fin; and

filling the trench with a material to form the gate.

14. The method of claim 13 , wherein the material comprises at least one of polysilicon and metal.

15. The method of claim 13 , wherein the fin comprises silicon.

16. The method of claim 15 , wherein etching the protrusion and the oxide layer comprises:

etching selective to silicon.

17. The method of claim 15 , wherein the trench crosses over the fin transverse to the fin.

18. The method of claim 15 , further comprising:

forming an anti-reflective coating over the oxide layer prior to etching away at least a portion of the oxide layer to form the protrusion.

19. The method of claim 18 , wherein etching away at least a portion of the oxide layer further comprises:

depositing and patterning a layer of photo-resist material over the anti-reflective coating.