A vertical memory device includes a substrate, first and second sub-semiconductor patterns, first and second common source contacts, and first and second cell structures. The substrate includes a first region and a second region having a same length as the first region in a first direction, the first region having a first width in a second direction perpendicular to the first direction, and the second region having a second width in the second direction that is less than the first width. The first sub-semiconductor pattern covers the first region, and a portion of the first sub-semiconductor pattern has a first thickness. The second sub-semiconductor pattern covers the second region and has a second thickness that is less than the first thickness. The first and second common source contacts are disposed on edges in the second direction of the first and second patterns, respectively.