3D MEMORY WITH VERTICAL BIT LINES AND STAIRCASE WORD LINES AND VERTICAL SWITCHES AND METHODS THEREOF

摘要

A vertical switching layer of a 3D memory device serves to switch a set of vertical local bit lines to a corresponding set of global bit lines, the vertical switching layer being a 2D array of TFT channels of vertical thin-film transistors (TFTs) aligned to connect to an array of local bit lines, each TFT switching a local bit line to a corresponding global bit line. The TFTs in the array have a separation of lengths Lx and Ly along the x- and y-axis respectively such that a gate material layer forms a surround gate around each TFT in an x-y plane and has a thickness that merges to form a row select line along the x-axis while maintaining a separation of length Ls between individual row select lines. The surround gate improves the switching capacity of the TFTs.