Three-dimensional memory device having conductive support structures and method of making thereof

Abstract

An alternating stack of insulating layers and sacrificial material layers is formed over a horizontal layer, which can be formed over a lower-interconnect-level dielectric material layer overlying a substrate. Structural integrity of insulating layers vertically spaced from one another by backside recesses during replacement of sacrificial material layers with electrically conductive layers can be enhanced by forming electrically inactive laterally-insulated support structures concurrently with formation of laterally-insulated conductive via structures that vertically extend through each layer in the alternating stack and through the horizontal layer and to lower-interconnect-level metal interconnect structures. Alternatively or additionally, the structural integrity of insulating layers during the replacement process can be enhanced by M×N array of semiconductor-containing support structures that extend through staircase region and having same materials as memory stack structures.