A three-dimensional semiconductor memory device may include a stack including gate electrodes sequentially stacked on a substrate and a vertical structure penetrating the stack. The vertical structure may include a vertical channel portion, a charge storing structure on an outer side surface of the vertical channel portion, and a pad. The pad may include a first pad portion disposed in an internal space surrounded by the vertical channel portion and a second pad portion provided on the first pad portion and extended onto a top surface of the charge storing structure. A portion of the first pad portion may be disposed at the same level as an uppermost electrode of the gate electrodes.