A semiconductor device includes first and second substrates including cell and peripheral circuit regions, first and second gate electrode structures, first and second channels, and first to third transistors. The first and second gate electrode structures include first and second gate electrodes in a vertical direction. The first and second channel extend through the first and second gate electrode structures. The first transistor is on the peripheral circuit region. The second gate electrode structure is on the first gate electrode structure and the first transistor. The second and third transistors are on the second gate electrode structure. The second substrate is on the second and third transistors. The first and second channels do not directly contact each other, are electrically connected with each other, and receive electrical signals from the second transistor. The first and third transistors apply electrical signals to the first and second gate electrode structures.