Three-dimensional memory device with drain-select-level isolation structures and method of making the same

Abstract

A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over a substrate, first memory opening fill structures extending through the alternating stack, where each of the first memory opening fill structures includes a respective first drain region, a respective first memory film, a respective first vertical semiconductor channel contacting an inner sidewall of the respective first memory film, and a respective first dielectric core, and a drain-select-level isolation structure having a pair of straight lengthwise sidewalls that extend along a first horizontal direction and contact straight sidewalls of the first memory opening fill structures. Each first vertical semiconductor channel includes a tubular section that underlies a horizontal plane including a bottom surface of the drain-select-level isolation structure and a semi-tubular section overlying the tubular section.