An integrated circuit device includes a substrate, a peripheral wiring circuit that includes a bypass via and is disposed on the substrate, a peripheral circuit that includes an interlayer insulating layer surrounding at least a portion of the peripheral wiring circuit, and a memory cell array disposed on and overlapping the peripheral circuit. The memory cell array includes a base substrate, a plurality of gate lines disposed on the base substrate, and a plurality of channels penetrating the plurality of gate lines. The integrated circuit device further includes a barrier layer interposed between the peripheral circuit and the memory cell array. The barrier layer includes a bypass hole penetrating from a top surface to a lower surface of the barrier layer. The bypass via is disposed in the bypass hole.