Nonvolatile semiconductor memory device with no decrease in read margin and method of reading the same

Abstract

According to one embodiment, a plurality of memory cells, each composed of a variable-resistance element and a diode, are arranged at the intersections of a plurality of word lines and a plurality of bit lines. The sense amplifier compares a voltage corresponding to current in a memory cell selected from the plurality of memory cells with a reference voltage to detect data read from the selected memory cell. The controller generates the reference voltage according to the logical value of a signal output from the sense amplifier. The controller, before detecting data in the memory cell, adjusts the reference voltage on the basis of current flowing in one of a plurality of bit lines connected to a plurality of memory cells in a half-selected state detected by the sense amplifier.