Patent ID: 7203095

Claim:
A method for determining programming voltage in order to set the drain voltage with an optimum level applied to the programming operation for memory cells by hot carrier injection in a nonvolatile memory which includes the memory cells for storing information on the basis of the number of carriers accumulated between the control gate and the channel region, the method comprising the steps of: setting the drain voltage to an initial setting level; programming the memory cell through applying the drain voltage and a gate voltage to the drain and the control gate respectively of the memory cell for a predetermined programming time; shifting the drain voltage to another setting level; reprogramming the memory cell with the another setting level of the drain voltage determined by the shifting step; measuring the threshold voltage of the memory cell after the programming operation in the programming step or the reprogramming step; and determining a differential represented by a ratio of a change in the threshold voltage to a change in the drain voltage at the threshold voltage after the reprogramming step, wherein when the differential determined in the determining step and the threshold voltage measured in the measuring step remain within their respective permissible ranges, the setting level determined in the shifting step is defined as an optimum level of the drain voltage.