Nonvolatile memory device and method of making the same

Abstract

A nonvolatile memory device includes a substrate, a structure including a stack of alternately disposed layers of conductive and insulation materials disposed on the substrate, a plurality of pillars extending through the structure in a direction perpendicular to the substrate and into contact with the substrate, and information storage films interposed between the layers of conductive material and the pillars. In one embodiment, upper portions of the pillars located at the same level as an upper layer of the conductive material have structures that are different from lower portions of the pillars. In another embodiment, or in addition, upper string selection transistors constituted by portions of the pillars at the level of an upper layer of the conductive material are programmed differently from lower string selection transistors.