A semiconductor device includes a first element separation structure, a second element separation structure, and a third element separation structure sequentially disposed along a first direction and extending in a second direction intersecting the first direction; a first active pattern extending in the first direction between the first element separation structure and the second element separation structure; a second active pattern extending in the first direction between the second element separation structure and the third element separation structure and separated from the first active pattern by the second element separation structure; a first gate electrode extending in the second direction on the first active pattern; and a plurality of second gate electrodes extending in the second direction on the second active pattern, wherein a width of the first active pattern in the second direction is greater than a width of the second active pattern in the second direction.