Fin formation for semiconductor device

1. A method of fabricating a semiconductor device, the method comprising:

forming a plurality of semiconductor fins disposed on a semiconductor substrate, wherein at least one of the fins is an unwanted fin comprising a semiconductor material;

providing a conformal protective layer over the plurality of semiconductor fins;

forming a mask having an opening over the unwanted fin;

removing a portion of the unwanted fin to form a trench exposing a surface of the substrate and a sidewall of a fin spike, a portion of the conformal protective layer remaining over a topmost surface of the fin spike, wherein a second sloped portion of the unwanted fin that is not removed defines the fin spike;

oxidizing the fin spike to form an oxidized semiconductor material;

removing the oxidized semiconductor material to expose a fin base, wherein the exposed fin base comprises a cavity in the substrate; and

removing the portion of the conformal protective layer.

2. The method of claim 1 , wherein the unwanted fin comprises a hard mask disposed below the conformal protective layer, and

wherein the removing the portion of the unwanted fin to expose the fin spike comprises removing the hard mask from the unwanted fin exposed through the opening.

3. The method of claim 1 , wherein the removing the portion of the unwanted fin to expose the fin spike exposes the semiconductor material of the unwanted fin.

4. The method of claim 1 , wherein the removing the oxidized semiconductor material to expose the fin base comprises removing the oxidized semiconductor material of the unwanted fin.

5. The method of claim 1 , wherein the conformal protective layer protects remaining fins of the plurality of semiconductor fins while oxidizing the fin spike to form the oxidized semiconductor material and while removing the oxidized semiconductor material of the unwanted fin.

6. The method of claim 1 , further comprising:

removing the conformal protective layer from the remaining fins, after the removing the oxidized semiconductor material of the unwanted fin.

7. The method of claim 1 , wherein the oxidizing is conducted by steam oxidation.

8. The method of claim 1 , wherein both the unwanted fin and the semiconductor substrate comprise a same semiconductor material.

9. The method of claim 8 , wherein the semiconductor material comprises silicon.

10. The method of claim 1 , wherein the oxidized semiconductor material comprises silicon oxide.

11. The method of claim 1 , wherein the providing the conformal protective layer comprises:

providing the conformal protective layer over the plurality of semiconductor fins with a thickness less than or equal to about 5 nanometers.

12. The method of claim 1 , wherein the patterning further comprises providing a photoresist layer over a planarization material, and

wherein the opening over the unwanted fin extends through the photoresist layer.

13. The method of claim 12 , wherein the patterning further comprises:

providing an anti-reflective coating between the planarization material and the photoresist layer, and

wherein the opening over the unwanted fin extends through the photoresist layer and the anti-reflective coating, at least partially into the planarization material.

14. The method of claim 13 , wherein the unwanted fin comprises a hard mask disposed below the conformal protective layer, and

wherein the removing the portion of the unwanted fin to expose the fin spike comprises removing the hard mask from the unwanted fin exposed through the opening.

15. The method of claim 14 , wherein the removing the portion of the unwanted fin to expose the fin spike exposes the semiconductor material of the unwanted fin; and

wherein the removing the oxidized semiconductor material to expose the fin base comprises removing the oxidized semiconductor material of the unwanted fin, wherein the conformal protective layer protects remaining fins of the plurality of semiconductor fins during removing the oxidized semiconductor material of the unwanted fin.

16. The method of claim 15 , further comprising:

removing the conformal protective layer from the remaining fins, after the removing the oxidized semiconductor material of the unwanted fin.

17. A method of fabricating a semiconductor device, the method comprising:

forming a plurality of semiconductor fins disposed on a semiconductor substrate, wherein at least one of the fins is an unwanted fin comprising a semiconductor material;

providing a conformal protective layer over the plurality of semiconductor fins;

forming a mask having an opening over the unwanted fin;

removing a portion of the conformal protective layer over the unwanted fin exposed through the opening;

removing a portion of the unwanted fin exposed through the opening to form a trench exposing a surface of the substrate and a sidewall of a fin spike, a second portion of the conformal protective layer remaining over a topmost surface of the fin spike, wherein a second portion of the unwanted fin that is not removed defines a sloped portion of the fin spike;

oxidizing the fin spike to form an oxidized semiconductor material;

removing the oxidized semiconductor material to expose a fin base, wherein the exposed fin base comprises a cavity in the substrate; and

removing the second portion of the conformal protective layer.

18. The method of claim 17 , wherein the unwanted fin comprises a hard mask disposed under the conformal protective layer, and

wherein the removing the portion of the unwanted fin to expose the fin spike comprises dry-etching the hard mask from the unwanted fin exposed through the opening.

19. The method of claim 18 , wherein the removing the portion of the unwanted fin to expose the fin spike exposes the semiconductor material of the unwanted fin; and

wherein the method further comprises:

selectively wet-etching the semiconductor material of the unwanted fin, wherein the conformal protective layer protects remaining fins of the plurality of fins during the selective wet-etching of the semiconductor material of the unwanted fin; and

removing the conformal protective layer from the remaining fins, after the removing the oxidized semiconductor material of the unwanted fin.