PURPOSE: To form a high concentration region in a channel region with high accuracy, to shape a thin select gate insulating film having high quality easily and to change a PACMOS memory into low program voltage by implanting ions into the high concentration region through a gate insulating film and a polycrystalline silicon film formed on the gate insulating film.

CONSTITUTION: A floating gate electrode 4 consisting of polycrystalline silicon is formed, and the electrode 4 is oxidized. A thin polycrystalline silicon film 11 is shaped so as to coat a channel L1. A high concentration region 7 is formed through ion implantation while using the floating gate electrode 4, a side-surface oxide film 9' for the floating gate electorde 4 and the side surface of the thin polycrystalline silicon film 11 as masks. The high concentration region 7 is shaped so as not to be infiltrated into a second channel region L2 by properly selecting the thickness of the thin polycrystalline silicon film 11 and the acceleration energy of ion implantation. Consequently, a sharp potential gap can be obtained on a boundary between the channel L1 and the channel L2 in the surfaces of the channels on a program. Accordingly, the rate of generation of hot electrons is increased, and program voltage is lowered.