A method of manufacturing a vertical memory device is disclosed. In the method, a plurality of insulation layers and a plurality of first sacrificial layers are alternately stacked on a substrate. A plurality of holes is formed through the plurality of insulation layers and first sacrificial layers. A plasma treatment process is performed to oxidize the first sacrificial layers exposed by the holes. A plurality of second sacrificial layer patterns project from sidewalls of the holes. A blocking layer pattern, a charge storage layer pattern and a tunnel insulation layer pattern are formed on the sidewall of the holes that cover the second sacrificial layer patterns. A plurality of channels is formed to fill the holes. The first sacrificial layers and the second sacrificial layer patterns are removed to form a plurality of gaps exposing a sidewall of the blocking layer pattern. A plurality of gate electrodes is formed to fill the gaps.