A semiconductor device and an electronic system, the device including a substrate including a cell array region and a connection region; a stack including electrodes vertically stacked on the substrate; a source conductive pattern on the cell array region and between the substrate and the stack; a dummy insulating pattern on the connection region and between the substrate and the stack; a conductive support pattern between the stack and the source conductive pattern and between the stack and the dummy insulating pattern; a plurality of first vertical structures on the cell array region and penetrating the electrode structure, the conductive support pattern, and the source structure; and a plurality of second vertical structures on the connection region and penetrating the electrode structure, the conductive support pattern, and the dummy insulating pattern.