Abstract: Disclosed is a semiconductor memory device including stacks on a substrate, a vertical channel portion connected to the substrate through each of the stacks, and a separation pattern disposed between the stacks. Each of the stacks may include a plurality of gate electrodes stacked on the substrate and insulating patterns interposed between the gate electrodes. Each of the gate electrodes may include a first metal pattern, which is disposed between the insulating patterns to define a recess region recessed toward the vertical channel portion, and a second metal pattern disposed in the recess region. The first and second metal patterns may contain the same metallic material and may have mean grain sizes different from each other.