There are provided a semiconductor memory device and a manufacturing method of the semiconductor memory device. A semiconductor memory device includes a lower stack structure on the substrate and including a plurality of lower layers stacked in a vertical direction, an intermediate stack structure on the lower stack structure and including a plurality of intermediate layers stacked in the vertical direction, a plurality of grooves in the contact region and penetrating the intermediate stack structure, the plurality of grooves exposing the lower stack structure at different depths, and a plurality of steps formed along sidewalls of the grooves.