Patent ID: 7330374

Claim:
A semiconductor memory device, comprising: memory cells, each of which has a place for accumulating an electrostatic charge and which stores data according to a charge amount of the place accumulating the electrostatic charge; wherein a memory cell storing data according to a charge amount of a place accumulating an electrostatic charge is used as a first reference cell which generates a voltage or current to be a judgment reference when data is read out from each of the memory cells; a second reference cell which generates a voltage or current to be a judgment reference when data is read out from the first reference cell is provided; and a threshold of the first reference cell is changed on the basis of the voltage or current generated by the second reference cell, wherein a plurality of second reference cells are used; and wherein, when the read operations of the second reference cells are performed on the basis of the first reference cell, the threshold of the first reference cell is adjusted based on 0/1 judgment results for each second reference cell.