A memory device may include multiple channel regions extending in a direction perpendicular to an upper surface of a substrate, a plurality of gate electrode layers and a plurality of insulating layers stacked on the substrate to be adjacent at least a portion of the plurality of channel regions, an interlayer insulating layer disposed on the plurality of gate electrode layers, a plurality of cell contact plugs passing through the interlayer insulating layer. Each of the plurality of cell contacts is connected to each of the plurality of gate electrode layers. A vertical insulating layer extends from the interlayer insulating layer disposed between the plurality of channel regions and the plurality of cell contact plugs and has a portion surrounded by at least one of the plurality of gate electrode layers.