A semiconductor device includes a semiconductor substrate, a metal gate structure, at least an epitaxial layer, an interlayer dielectric, at least a contact hole, at least a metal silicide layer and a fluorine-containing layer. The semiconductor substrate has at least a gate region and at least a source/drain region adjoining the gate region. The gate structure is disposed on the semiconductor substrate within the gate region. The epitaxial layer is disposed on the semiconductor substrate within the source/drain region. The interlayer dielectric covers the semiconductor substrate, the gate structure and the epitaxial layer. The contact hole penetrates the interlayer dielectric to reach the epitaxial layer. The metal silicide layer is formed in the epitaxial layer and is located on the bottom of the contact hole. The fluorine-containing layer is disposed on or in the epitaxial layer and is around sides of the metal silicide layer.