A memory device and a method of manufacturing the memory device includes a stacked structure having a cell region and a slimming region therein and formed by alternately stacking insulating layers and conductive layers, vertical channel structures formed to pass through the stacked structure in the cell region, support structures formed to pass through the stacked structure in the slimming region, and having different heights depending on a stacked height of the slimming region, each of the support structures having the vertical channel structure, an etching prevention layer formed over the stacked structure and including carbon, and contact plugs formed to pass through the etching prevention layer and coupled to the conductive layers.