A semiconductor memory device includes a stack structure having a plurality of layers vertically stacked on a substrate, each layer including, a first bit line and a gate line extending in a first direction, a first semiconductor pattern extending in a second direction between the first bit line and the gate line, the second direction intersecting the first direction, and a second semiconductor pattern adjacent to the gate line across a first gate insulating layer, the second semiconductor pattern extending in the first direction, a first word line adjacent to the first semiconductor pattern and vertically extending in a third direction from the substrate, a second bit line connected to an end of the second semiconductor pattern and vertically extending in the third direction from the substrate, and a second word line connected to another end of the second semiconductor pattern and vertically extending in the third direction.