Patent ID: 7187588

Claim:
A semiconductor storage device comprising: a first conductivity type semiconductor substrate, a first conductivity type well region provided in a semiconductor substrate, or a first conductivity type semiconductor film disposed on an insulator; a gate insulating film formed on the first conductivity type semiconductor substrate, the first conductivity type well region provided in the semiconductor substrate, or the first conductivity type semiconductor film disposed on the insulator; a single gate electrode formed on the gate insulating film; two charge holding portions formed on sides of side walls of the single gate electrode; a channel region disposed under the single gate electrode; and second conductivity type diffusion layer regions disposed on both sides of the channel region, wherein the charge holding portions are structured so as to change a current amount flowing between one of the second conductivity type diffusion layer regions and the other of the second conductivity type diffusion layer regions when voltage is applied to the gate electrode by an amount of electric charges stored in the charge holding portions, a reference voltage is applied to the other of the second conductivity type diffusion layer regions, a first voltage is applied to the one of the second conductivity type diffusion layer regions, a second voltage is applied to the gate electrode such that carriers are injected into the the charge holding portion existing on the side of the one of the second conductivity type diffusion layer regions, the second conductivity type diffusion layer regions are respectively offset relative to edges of the single gate electrode, no electrode exists on each of the two charge holding portions, and the two charge holding portions are respectively located above part of the channel region and part of each of the second conductivity type diffusion layer regions.