Three-dimensional memory device having on-pitch drain select gate electrodes and method of making the same

Abstract

An array of memory stack structures extends through an alternating stack of insulating layers and electrically conductive layers. The drain-select-level assemblies may be provided by forming drain-select-level openings through a drain-select-level sacrificial material layer, and by forming a combination of a cylindrical electrode portion and a first gate dielectric mayin each first drain-select-level opening while forming a second gate dielectric directly on a sidewall of each second drain-select-level opening in a second subset of the drain-select-level openings. A strip electrode portion is formed by replacing the drain-select-level sacrificial material layer with a conductive material. Structures filling the second subset of the drain-select-level openings may be used as dummy structures at a periphery of an array. The dummy structures are free of gate electrodes and thus prevents a leakage current therethrough.