Quasi-volatile memory with reference bit line structure

Abstract

A semiconductor memory device is implemented as strings of storage transistors, where the storage transistors in each string have drain terminals connected to a bit line and gate terminals connected to respective word lines. In some embodiments, the semiconductor memory device includes a reference bit line structure to provide a reference bit line signal for read operation. The reference bit line structure configures word line connections to provide a reference bit line to be used with a storage transistor being selected for read access. The reference bit line structure provides a reference bit line having the same electrical characteristics as an active bit line and is configured so that no storage transistors are selected when a word line is activated to access a selected storage transistor associated with the active bit line.