A semiconductor device including an active pattern having a channel recess portion, and a method of fabricating the same, are disclosed. In one embodiment, the semiconductor device includes an active pattern including first active regions and a second active region interposed between the first active regions. The active pattern protrudes above a surface of a semiconductor substrate and includes a channel recess portion above the second active region and between the first active regions. A device isolation layer surrounds the active pattern and has a groove exposing side walls of the recessed second active region. A distance between opposing side walls of the first active regions exposed by the channel recess portion is greater than a distance between side walls of the groove. A gate pattern is located in the channel recess portion and extends along the groove.