Provided is a three-dimensional semiconductor memory device. The three-dimensional semiconductor memory device includes a substrate that has a cell array region including a pair of sub-cell regions and a strapping region interposed between the pair of sub-cell regions. A Plurality of sub-gates are sequentially stacked on the substrate in each of the sub-cell regions, and interconnections are electrically connected to extensions of the stacked sub-gates, respectively, which extend into the strapping region. Each of the interconnections is electrically connected to the extensions of the sub-gate which are disposed in the pair of the sub-cell regions, respectively, and which are located at the same level.