PROBLEM TO BE SOLVED: To reduce the operating voltage and thereby facilitate microfabrication of an element by storing information through a change in threshold voltage caused by carriers entrapped into a gate oxide film.
SOLUTION: When a voltage is applied between a substrate electrode 209 and a gate electrode 208 or between a drain electrode 205 and the electrode 208, the generated electric field thereby causes a tunnel current to flow from a drain junction region 203 or a substrate 201 to inject carriers into a corner- structured gate oxide film 206. At this time, the carriers can be entrapped efficiently into the film 206 by controlling the applied voltage. The carriers are continuously entrapped at the corner-structured portion, without being released even if a heat treatment is carried out at high temperatures. Thus, whether or not the carriers entrapped into the film 206 causes a change in the threshold voltage of a MOSFET, and this change is stored as information.