A semiconductor memory device includes a stack structure comprising a plurality of layers vertically stacked on a substrate, each layer including a semiconductor pattern, a gate electrode extending in a first direction on the semiconductor pattern, and a data storage element electrically connected to the semiconductor pattern, a plurality of vertical insulators penetrating the stack structure, the vertical insulators arranged in the first direction, and a bit line provided at a side of the stack structure and extending vertically. The bit line electrically connects the semiconductor patterns which are stacked. Each of the vertical insulators includes first and second vertical insulators adjacent to each other. The gate electrode includes a connection portion disposed between the first and second vertical insulators.