A semiconductor device includes a plurality of semiconductor patterns stacked to be spaced apart from each other in a first direction, perpendicular to an upper surface of a substrate, and extending in a second direction, parallel to the upper surface of the substrate, a plurality of first conductive patterns extending in a third direction, perpendicular to the first direction and the second direction, on the plurality of semiconductor patterns, a plurality of second conductive patterns extending in the first direction on the substrate, a plurality of capacitors electrically connected to the plurality of semiconductor patterns, respectively, and at least one epitaxial layer disposed to be in contact with at least one of both end surfaces of at least one of the plurality of semiconductor patterns and including an impurity.