PURPOSE: To prevent the titled device from leakage of holding electric charge, and to eliminate generation of memory error by a method wherein the upper part of an electric charge storage region consisting of a floating gate to store the desired informations by holding electric charge is covered with an Al wiring layer having X-rays shielding function.

CONSTITUTION: Thick field oxide films 2 are formed at the circumferential part of an Si substrate 1, a first thin gate SiO2 film 3 is adhered on the surface of the substrate 1 surrounded with the oxide film thereof, and the floating gate 4 consisting of polycrystalline Si is deposited thereon to form the electric charge storage region. Then a second gate SiO2 film 5 is adhered thereon, a polycrystalline Si control gate 6 is provided on the whole surface containing the second gate film thereof, and source.drain regions 7, 8 are formed by diffusion positioning in the substrate 1 on both the sides of the gate 6. After then, the upper part of the gate 6 is covered with a thick interlayer insulating film 9, the Al wiring layer 11 is adhered thereon cutting the gate 4 at right angles, and a part of the wiring layer thereof positioning on the gate 4 is used as the X-rays shielding part 12.