The channel of each nonvolatile semiconductor memory element has a plate-like shape, and a charge accumulating layer is formed on one face of the channel region, with an insulating film being interposed in between. A control gate electrode is then formed on the charge accumulating layer, with another insulating film being interposed in between. Another control gate electrode is formed on the other face of the channel region, with yet another insulating film being interposed in between. The plate-like semiconductor region is designed to have a thickness smaller than twice the largest depletion layer thickness determined by the impurity concentration. In this manner, variations of the threshold voltages varying with the voltage of the control gate electrodes can be made smaller than the minimum value in conventional elements. As a result, nonvolatile semiconductor memory elements that have higher controllability over threshold voltages and can lower the power supply voltage so as to reduce the power consumption can be provided.