PURPOSE: To pull out an electron without passing through a junction, control a charge trap to a gate oxide film and prevent threshold fluctuation.

CONSTITUTION: The cell structure of a semiconductor storage device is constituted by arranging a floating gate 15 between a semiconductor substrate 11 of one conductivity type and a control gate 12 through an oxide film and by forming a source area 16 of another conductivity type and a drain area 17 in the semiconductor substrate under the floating gate 15. Prescribed subgates 18a and 18b are arranged at a very short distance from the gate edges 15a and 15b of the floating gate 15 and oxide films are provided between the gate edges 15a, 15b and the subgates 18a, 18b.