A vertical memory device includes a gate electrode structure on a substrate, and a channel. The gate electrode structure includes gate electrodes spaced apart from each other in a vertical direction substantially perpendicular to an upper surface of the substrate. The channel extends through the gate electrode structure in the vertical direction on the substrate. The channel includes a first portion having a slanted sidewall with respect to the upper surface of the substrate and a second portion contacting an upper surface of the first portion and having a slanted sidewall with respect to the upper surface of the substrate. A width of an upper surface of the second portion is less than a width of the upper surface of the first portion. An impurity region doped with carbon or p-type impurities is formed at an upper portion of the substrate. The channel contacts the impurity region.