A semiconductor device includes a substrate including a first active region and a second active region, the first active region having a conductivity type that is different than a conductivity type of the second active region, and the first active region being spaced apart from the second active region in a first direction, gate electrodes extending in the first direction, the gate electrodes intersecting the first active region and the second active region, a first shallow isolation pattern disposed in an upper portion of the first active region, the first shallow isolation pattern extending in the first direction, and a deep isolation pattern disposed in an upper portion of the second active region, the deep isolation pattern extending in the first direction, and the deep isolation pattern dividing the second active region into a first region and a second region.