A semiconductor device is provided. The semiconductor device includes a substrate, a first active pattern, which extends in a first direction on the substrate, a second active pattern, which extends in the first direction on the substrate and is spaced apart from the first active pattern by a first pitch in a second direction different from the first horizontal direction, a third active pattern, which extends in the first direction on the substrate and is spaced apart from the second active pattern by a second pitch greater than the first pitch in the second direction, a field insulating layer, which borders side walls of each of the first to third active patterns, a dam, which is between the first active pattern and the second active pattern on the field insulating layer, the region between the second active pattern and the third active pattern being free of the dam, a gate electrode, which extends in the second direction, and has a first portion on the first active pattern, a second portion on the second active pattern, and a third portion on the third active pattern, a first work function layer between the first portion of the gate electrode and the dam, and a second work function layer between the second portion of the gate electrode and the dam.