A semiconductor device includes a memory cell region including a plurality of memory cells disposed on a first semiconductor substrate and including gate electrodes stacked to be spaced apart from each other on the first semiconductor substrate and channel structures passing through the gate electrodes and connected to the first semiconductor substrate, a peripheral circuit region including a first conductivity-type impurity, disposed on a second semiconductor substrate having an upper surface facing each other in a first direction, perpendicular to an upper surface of the first semiconductor substrate, and including peripheral circuits controlling the plurality of memory cells, wherein the peripheral circuits include a plurality of well regions formed in the second semiconductor substrate, an ion implantation region disposed between the plurality of well regions and including the first conductivity-type impurity, and a plurality of antenna diodes, and at least one of the plurality of antenna diodes overlaps the ion implantation region in the first direction. Accordingly, in the semiconductor device according to an exemplary embodiment of the present inventive concept, an antenna diode may be inserted, while minimizing an increase in an interval between the plurality of well regions, and further, peripheral circuits may be integrated and wiring complexity may be reduced.