A nonvolatile memory device includes a first structure and a second structure bonded to the first structure. The second structure includes a low-resistance conductive layer, a common source line layer on the low-resistance conductive layer, a stack structure above the common source line layer, a plurality of channel structures passing through a cell region of the stack structure and contacting the common source line layer, a dummy channel structure passing through a step region of the stack structure and contacting the common source line layer, a second insulating structure on the stack structure, a plurality of second bonding pads on the second insulating structure, and a second interconnect structure in the second insulating structure.