Nonvolatile semiconductor memory device, three-dimensional semiconductor device, and method of manufacturing the same

Abstract

A three-dimensional semiconductor device includes a semiconductor substrate, a plurality of conductive layers and insulating layers, and a plurality of contacts. The plurality of conductive layers and insulating layers are stacked alternately above the semiconductor substrate. The plurality of contacts extend in a stacking direction of the plurality of conductive layers and insulating layers. The plurality of conductive layers form a stepped portion having positions of ends of the plurality of conductive layers gradually shifted from an upper layer to a lower layer. The plurality of contacts are connected respectively to each of steps of the stepped portion. The stepped portion is formed such that, at least from an uppermost conductive layer to a certain conductive layer, the more upwardly the conductive layer is located, the broader a width of the step is.