Provided are a semiconductor device and a method of fabricating the same. The device may include an active pattern protruding from a substrate, gate structures crossing the active pattern, and a source/drain region provided between adjacent ones of the gate structures. The source/drain region may include a source/drain epitaxial layer in a recessed region, which is formed in the active pattern between the adjacent ones of the gate structures. Further, an impurity diffusion region may be provided in the active pattern to enclose the source/drain epitaxial layer along inner surfaces of the recessed region.