| 摘要 |
<p>PURPOSE:To improve the readout speed by a method wherein the drain voltage at the time of readout, which guarantees the prescribed soft write resistance, is decided lower, whreby the memory cell is driven by the decided voltage. CONSTITUTION:In a floating gate type non-volatile semiconductor memory using a transistor of a floating gate structure as the memory cell, a drain voltage dependence characteristic in the time to be required for changing the threshold voltage by a constant amount in a region having a drain voltage higher than a drain voltage which is impressed on the drain 17 of the above transistor at the time of normal data readout is found out, a drain voltage to be required by 10 years for a change in the threshold voltage of a constant amount which can be found out by a lineal extrapolation from this characteristic is found out and a voltage higher by about 0.25 V than this found drain voltage is impressed on the drain of the above transistor at the time of normal data readout. Thereby, by driving the memory cell by the decided voltage, the readout speed can be improved.</p> |
