Provided is a three-dimensional semiconductor memory device including a first substrate that includes a cell array region and a connection region; first and second electrode layers that are sequentially stacked and spaced apart from each other on the first substrate, and an end portion of the first electrode layer and an end portion of the second electrode layer are offset from each other on the connection region; a first cell contact penetrating the second electrode layer and the first electrode layer such as to be connected to the second electrode layer on the connection region; and a first contact dielectric pattern between the first cell contact and the first electrode layer. The first cell contact includes columnar part that vertically extends from a top surface of the first substrate, and a connection part that laterally protrudes from the columnar part and contacts the second electrode layer.