Provided herein may be a semiconductor memory device and a method of manufacturing the semiconductor memory device. The semiconductor memory device includes a source structure, a stacked conductive layer that overlaps with the source structure, a first select conductive layer and a second select conductive layer disposed between the source structure and the stacked conductive layer, a stacked insulating layer disposed between the first and second select conductive layers and the stacked conductive layer, and a separation insulating structure provided between the first select conductive layer and the second select conductive layer.