Structures of bottom select transistor for embedding 3d-nand in beol and methods

Abstract

A flash memory device includes a substrate, an electrode layer on a portion of the substrate, the electrode layer being a work function adjusting layer or a metal silicide layer, and a memory cell. The memory cell includes a channel structure on the electrode layer and having, from the inside to the outside in this order, a channel layer in contact with the electrode layer, a tunneling insulator layer surrounding the channel layer, a charge trapping layer surrounding the tunneling insulator layer, and a barrier layer surrounding the charge trapping layer, and a plurality of gate structures surrounding the channel structure along an axial direction of the channel structure. The flash memory device may be formed on a dielectric layer, and its fabrication process is thus compatible with back end of line processes.