Abstract
A non-volatile semiconductor memory device includes a non-volatile memory cell array and a control circuit for controlling writing-in to the memory cell array. In the stage before an erasing pulse adding in an erasing process where data of written-in memory cells is erased, the control circuit detects a programming speed when writing-in to the memory cell array, determines a programming start voltage corresponding to the programming speed for every block or every word line, stores the determined programming start voltage in the memory cell array and reads-out the programming start voltage from the memory cell array to write-in predetermined data.