Nonvolatile semiconductor memory device of virtual-ground memory array with reliable data reading

摘要

A nonvolatile semiconductor memory device includes a virtual-ground memory array which includes a plurality of word lines and a plurality of bit lines, a row decoder which selectively activates one of the word lines, a column decoder which applies a sense potential to one of the bit lines, and couples all the remaining ones of the bit lines to a ground potential, and a sense amplifier which compares an electric current running through the one of the bit lines with a first reference current and a second reference current so as to sense a data state of two memory cells that are connected to the one of the word lines and share the one of the bit lines, the sensed data state including a first state in which both of the two memory cells are “0”, a second state in which both of the two memory cells are “1”, and a third state in which one of the two memory cells is “1” and another of the two memory cells is “0”.