A semiconductor memory device, and a manufacturing method of the semiconductor memory device, includes a peripheral transistor, a first insulating layer covering the peripheral transistor, a source layer on the first insulating layer, and a stack structure on the source layer. The semiconductor memory device also includes a peripheral contact structure penetrating the stack structure and the source layer, the peripheral contact structure being electrically connected to the peripheral transistor. The stack structure includes a stepped structure including a step side surface and a step top surface. The peripheral contact structure is in contact with the step side surface.