Semiconductor device and method of forming vertical structure

1. A method of forming a vertical structure, comprising:

providing a substrate;

providing the vertical structure having a source, a channel, and a drain over the substrate;

shrinking the source and the channel by oxidation;

forming a metal layer over the drain of the vertical structure; and

annealing the metal layer to form a silicide over the drain of the vertical structure;

wherein shrinking the source and the channel by oxidation includes:

forming a first oxide layer over the vertical structure,

forming a nitride layer over the first oxide layer, the nitride layer including an upper horizontal portion and a lower horizontal portion,

forming a second oxide layer over the nitride layer,

performing CMP on the first oxide layer and the second oxide layer and the upper portion of the nitride layer, and stopping at the lower horizontal portion of the nitride layer, and

etching the lower horizontal portion of the nitride layer and a portion of the first oxide layer to expose the drain.

2. The method of claim 1 , wherein providing the vertical structure having the source, the channel, and the drain over the substrate further comprises providing the vertical structure having a hard mask over the drain for protecting a top of the drain.

3. The method of claim 1 , wherein shrinking the source and the channel further includes:

forming a spacer adjacent to the drain;

etching the first oxide layer to expose the channel and the source;

shrinking, by oxidation, the source and the channel substantially without shrinking the drain covered by the spacer;

removing the spacer; and

removing oxidized portions of the source and the channel.

4. The method of claim 1 , further comprising:

forming silicide over the source;

forming a first interlayer dielectric over the source;

forming a high-k dielectric layer over the channel;

forming a metal gate layer over the high-k dielectric layer;

forming a second interlayer dielectric over the metal gate layer; and

forming an etch stop layer to cover a portion of the sidewall of the drain.

5. The method of claim 1 , wherein forming the metal layer over the drain of the vertical structure further comprises forming a metal layer over a top and a sidewall of the drain of the vertical structure.

6. The method of claim 5 , wherein annealing the metal layer to form silicide over the drain of the vertical structure further comprises annealing the metal layer to form silicide over the top and the sidewall of the drain of the vertical structure.

7. The method of claim 1 , wherein, before the shrinking, the source and the channel are as wide as the drain, and the shrinking leaves an oxidation portion on side surfaces of the source and the channel.

8. The method of claim 7 , further comprising:

removing the oxidized portions of the source and the channel, leaving the source and the channel narrower than the drain.

9. The method of claim 8 , further comprising forming:

a silicide layer over a horizontal surface of the source;

a first interlayer dielectric layer over the silicide layer;

a high-k dielectric layer over the first interlayer dielectric layer;

a metal gate layer over the high-k dielectric layer;

a second interlayer dielectric over the metal gate layer; and

an etch stop layer that overlies a vertical surface of the drain.

10. The method of claim 9 , wherein a horizontal surface of the high-k dielectric layer overlies a horizontal surface of the source, and a vertical surface of the high-k dielectric layer overlies a vertical surface of the source.

11. The method of claim 10 , wherein a horizontal surface of the metal gate layer overlies a horizontal surface of the high-k dielectric layer, and a vertical surface of the metal gate layer overlies a vertical surface of the high-k dielectric layer.

12. The method of claim 11 , wherein a horizontal surface of the second interlayer dielectric overlies a horizontal surface of the metal gate layer, and a vertical surface of the second interlayer dielectric layer overlies a vertical surface of the metal gate layer.

13. The method of claim 11 , further comprising, after the forming of the etch stop layer:

etching back the etch stop layer to expose a portion of the sidewall of the drain.

14. The method of claim 1 , wherein the vertical structure is a first vertical structure, the drain is a first drain, and the method further comprises:

providing, over the substrate, a second vertical structure having a second drain and a third vertical structure having a third drain.

15. The method of claim 14 , further comprising:

forming the metal layer over the second drain and the second drain, such that the annealing of the metal layer forms a continuous silicide layer that extends over the first, second and third drains.

16. The method of claim 15 , further comprising:

removing a section, of the silicide layer, that is between the second and third drains.

17. The method of claim 4 , wherein a horizontal surface of the high-k dielectric layer overlies a horizontal surface of the source, and a vertical surface of the high-k dielectric layer overlies a vertical surface of the source.

18. The method of claim 17 , wherein a horizontal surface of the metal gate layer overlies the horizontal surface of the high-k dielectric layer, and a vertical surface of the metal gate layer overlies the vertical surface of the high-k dielectric layer.

19. The method of claim 18 , wherein a horizontal surface of the second interlayer dielectric overlies the horizontal surface of the metal gate layer, and a vertical surface of the second interlayer dielectric layer overlies the vertical surface of the metal gate layer.

20. A method comprising:

providing, over a substrate, a vertical structure having a source, a channel, and a drain;

shrinking the source and the channel by oxidation;

forming a metal layer over the drain of the vertical structure; and

annealing the metal layer to form a silicide over the drain of the vertical structure;

wherein shrinking the source and the channel comprises:

forming a first oxide layer over the vertical structure,

forming a nitride layer over the first oxide layer,

forming a second oxide layer over the nitride layer,

performing CMP on the first oxide layer and the second oxide layer and stopping at a portion of the nitride layer,

etching the nitride layer and the first oxide layer to expose the drain,

forming a spacer adjacent to the drain,

etching the first oxide layer to expose the channel and the source,

shrinking the source and the channel substantially without shrinking the drain covered by the spacer,

removing the spacer, and

removing oxidized portions of the source and the channel.