Self-limiting silicide in highly scaled fin technology

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.