A vertical memory device includes first horizontal gate electrodes disposed on a substrate and spaced apart from each other in a first direction that is substantially perpendicular to an upper surface of the substrate. Each of the first horizontal gate electrodes extends in a second direction that is substantially parallel to the upper surface of the substrate. A vertical channel extends through the first horizontal gate electrodes in the first direction. A charge storage structure is disposed between the vertical channel and each of the first horizontal gate electrodes. A first vertical gate electrode extends through the first horizontal gate electrodes in the first direction. The first vertical gate electrode is electrically insulated from the first horizontal gate electrodes. A first horizontal channel is disposed at a portion of each of the first horizontal gate electrodes adjacent to the first vertical gate electrode.