Three-dimensional memory device containing variable thickness word lines with reduced length metal nitride diffusion barriers and methods for forming the same

Abstract

A semiconductor structure includes an alternating stack of insulating layers and electrically conductive layers, memory openings vertically extending through the alternating stack, memory opening fill structures located in the memory openings and including a respective vertical semiconductor channel and a respective vertical stack of memory elements, and a first backside trench fill structure and a second backside trench fill structure. Each of the electrically conductive layers includes a respective metal nitride liner and a respective metal fill material region. The respective metal fill material region includes a respective first-thickness portion having a respective first vertical thickness and a respective second-thickness portion having a respective second vertical thickness that is greater than the respective first vertical thickness.