Nonvolatile memory devices are provided and methods of manufacturing such devices. In the method, conductive layers and insulating layers are alternatingly stacked on a substrate. A first sub-active bar is formed which penetrates a first subset of the conductive layers and a first subset of the insulating layers. The first sub-active bar is electrically connected with the substrate. A second sub-active bar is formed which penetrates a second subset of the conductive layers and a second subset of the insulating layers. The second sub-active bar is electrically connected to the first sub-active bar. A width of a bottom portion of the second sub-active bar is less than a width of a top portion of the second sub-active bar.