SEMICONDUCTOR DEVICE

A semiconductor device includes gate electrodes stacked and spaced apart from each other in a first direction perpendicular to an upper surface of a substrate; interlayer insulating layers alternately stacked with the gate electrodes on the substrate; channel structures extending through the gate electrodes; and a separation region extending through the gate electrodes in the first direction and extending in a second direction perpendicular to the first direction, wherein each of the gate electrodes comprises a first conductive layer and a second conductive layer sequentially stacked, the second conductive layer including a metal nitride, and wherein the first conductive layer and the second conductive layer are each in physical contact with the separation region.