A semiconductor device includes; a substrate including a first region and a second region adjacent to the first region in a first direction, a pair of active patterns adjacently disposed on the substrate, wherein the pair of active patterns includes a first active pattern extending in the first direction and a second active pattern extending in parallel with the first active pattern, a first gate electrode on the first region and extending in a second direction that intersect the first direction across the first active pattern and the second active pattern, and a second gate electrode on the second region and extending in the second direction across the first active pattern and the second active pattern. A width of the first active pattern is greater on the first region than on the second region, a width of the second active pattern is greater on the first region than on the second region, and an interval between the first active pattern and the second active pattern is constant from the first region to the second region.