A three-dimensional (3D) nonvolatile memory device includes a vertical stack of nonvolatile memory cells on a substrate having a region of first conductivity type therein. A dopant region of second conductivity type is provided in the substrate. This dopant region forms a P-N rectifying junction with the region of first conductivity type and has a concave upper surface that is recessed relative to an upper surface of the substrate upon which the vertical stack of nonvolatile memory cells extends. An electrically insulating electrode separating pattern is provided, which extends through the vertical stack of nonvolatile memory cells and into the recess in the dopant region of second conductivity type.