A three-dimensional (3D) semiconductor memory device that includes a peripheral logic structure including peripheral logic circuits disposed on a semiconductor substrate and a first insulation layer overlapping the peripheral logic circuits, and a plurality of memory blocks spaced apart from each other on the peripheral logic structure. At least one of the memory blocks includes a well plate electrode, a semiconductor layer in contact with a first surface of the well plate electrode, a stack structure including a plurality of electrodes vertically stacked on the semiconductor layer, and a plurality of vertical structures penetrating the stack structure and connected to the semiconductor layer.