Patent ID: 7468908

Claim:
A non-volatile semiconductor memory device comprising: an electrically data rewritable non-volatile semiconductor memory cell; and a write circuit configured to write data to the memory cell by supplying a write voltage and a write control voltage to the memory cell to change the write state of the memory cell, the write circuit detecting if the write state of the memory cell has reached a first level or not and, upon detecting that the write state of the memory cell has reached the first level, the write circuit reducing a rate of change of the write state by changing the supply of the write control voltage, wherein the write circuit performs a write operation to sequentially increase the write voltage when writing data to the memory cell, the write circuit controls the rate of change of the reduced rate of change of the write state by sequentially increasing the write control voltage, and the rate of increase of the write voltage is greater than the rate of increase of the write control voltage.