PROBLEM TO BE SOLVED: To make possible the application of a micro memory cell and reduce an area of a memory chip, by impressing a voltage to a source, a drain diffusion layer step by step when electrons are pulled from a floating gate electrode. SOLUTION: When electrons are pulled out from a floating gate electrode, a positive voltage is impressed to a diffusion layer opposite to a diffusion layer where the electrons are to be pulled, thereby to decrease a maximum voltage impressed between a source terminal and a drain terminal. Further, a positive voltage is impressed to a control gate electrode of a memory cell where the electrons are not pulled and a diffusion layer not in a pull-out direction is let to float. A write/erasure method for the memory cell which is not restricted by a voltage decrease inviting a problematic punch-through current between the source and drain when the memory cell is microminiaturized, in other words, not restricted by a decrease of a punch-through voltage is obtained, and a memory chip can be very small.