A semiconductor device may include a substrate and a stacked structure in which a plurality of insulating layers and a plurality of interconnection layers are alternately stacked on the substrate. An isolation region may cross the stacked structure in a first direction. A plurality of first structures may extend into the stacked structure in a second direction perpendicular to the first direction. A plurality of first patterns may extend into the stacked structure in the second direction in the isolation region. Bottoms of the plurality of first patterns may be farther from an upper surface of the substrate than bottoms of the plurality of channel structures.