A non-volatile memory device includes an upper semiconductor layer including a first metal pad and vertically stacked on a lower semiconductor layer. The upper semiconductor layer includes a first memory group spaced apart from a second memory group in a first horizontal direction by a separation region, and the lower semiconductor layer includes a second metal and a bypass circuit underlying at least a portion of the separation region and configured to selectively connect a first bit line of the first memory group with a second bit line of the second memory group. The upper semiconductor layer is vertically connected to the lower semiconductor layer by the first metal pad and the second metal pad.