Epitaxial CoSi2 on MOS devices

An SixNy or SiOxNy liner is formed on a MOS device. Cobalt is then deposited and reacts to form an epitaxial CoSi2 layer underneath the liner. The CoSi2 layer may be formed through a solid phase epitaxy or reactive deposition epitaxy salicide process. In addition to high quality epitaxial CoSi2 layers, the liner formed during the invention can protect device portions during etching processes used to form device contacts. The liner can act as an etch stop layer to prevent excessive removal of the shallow trench isolation, and protect against excessive loss of the CoSi2 layer.