Self-limiting silicide in highly scaled fin technology

1. A method of forming a metal semiconductor alloy on a fin structure comprising:

forming a sacrificial gate structure on a channel portion of the fin structure;

forming a semiconductor material layer of a polycrystalline crystal structure material or amorphous crystal structure material on source and drain regions portions of the fin structure that have a single crystal semiconductor material after forming the sacrificial gate structure;

forming a metal including layer on the semiconductor material layer of the polycrystalline crystal structure material or the amorphous crystal structure material;

intermixing metal elements from the metal including layer with the semiconductor material layer to provide a metal semiconductor alloy contact on the fin structure, wherein a core of the fin structure of the single crystal semiconductor material is substantially free of the metal elements from the metal including layer; and

replacing the sacrificial gate structure with a functional gate structure after forming the metal semiconductor alloy contact.

2. The method of claim 1 , wherein the gate structure is a functional gate structure comprising at least one gate dielectric layer and at least one gate conductor layer.

3. The method claim 1 , wherein the functional channel includes at least one gate dielectric layer on the channel portion of the fin structure, and at least one gate conductor on the at least one gate dielectric.