A semiconductor device includes a device isolation pattern, a gate line, and an epitaxial pattern. The device isolation pattern is disposed in a semiconductor substrate to define an active area. The gate line intersects the active area. The epitaxial pattern fills a recess region in the active area at one side of the gate line and includes a different constituent semiconductor element than the semiconductor substrate. The recess region includes a first inner sidewall that is adjacent to the device isolation pattern and extends in the lengthwise direction of the gate, and a second inner sidewall that extends in the direction perpendicular to the lengthwise direction of the gate line. The active area forms the first inner sidewall of the recess, while the device isolation layer forms at least a portion of the second inner sidewall of the recess. The epitaxial pattern contacts the first inner sidewall and the second inner sidewall of the recess region.