A semiconductor device includes an isolation layer pattern, an epitaxial layer pattern, a gate insulation layer pattern and a gate electrode. The isolation layer pattern is formed on a substrate, and defines an active region in the substrate. The isolation layer pattern extends in a second direction. The epitaxial layer pattern is formed on the active region and the isolation layer pattern, and has a width larger than that of the active region in a first direction perpendicular to the second direction. The gate insulation layer pattern is formed on the epitaxial layer pattern. The gate electrode is formed on the gate insulation layer pattern.