Semiconductor devices and methods of manufacturing the same are provided. A disclosed semiconductor device includes: a semiconductor substrate; a gate insulating layer on the active region of the semiconductor substrate; a gate on the gate insulating layer; LDD regions on opposite sides of the gate insulating layer and located in the semiconductor substrate; source/drain regions on the LDD regions; and silicide layers on the surfaces of the gate and the source/drain regions. The source/drain regions are formed by doping impurities in a silicon layer grown by a selective epitaxy.