A semiconductor device including a substrate that includes first and second regions; a first active pattern on the first region, the first active pattern including first source/drain patterns and a first channel pattern between the first source/drain patterns; a second active pattern on the second region, the second active pattern including second source/drain patterns and a second channel pattern between the second source/drain patterns; and a first gate electrode on the first channel pattern and a second gate electrode on the second channel pattern, wherein a length of the first channel pattern is greater than a length of the second channel pattern, each of the first channel pattern and the second channel pattern includes a plurality of semiconductor patterns stacked on the substrate, and at least two semiconductor patterns of the first channel pattern are bent away from or toward a bottom surface of the substrate.