A semiconductor device includes a channel region, a source/drain region adjacent to the channel region, and a source/drain epitaxial layer. The source/drain epitaxial layer includes a first epitaxial layer epitaxially formed on the source/drain region, a second epitaxial layer epitaxially formed on the first epitaxial layer and a third epitaxial layer epitaxially formed on the second epitaxial layer. The first epitaxial layer includes at least one selected from the group consisting of a SiAs layer, a SiC layer and a SiCP layer.