A crystallized thin film semiconductor layer 42 is formed on the surface of an insulating substrate 41 of an insulating material such as quartz, sapphire or glass, and a tunneling oxide film 45 is formed thereon by CVD. Similarly to the second embodiment, a polycrystalline silicon film 46 as the first floating gate electrode is stacked on the tunneling oxide film 45, and a silicon nitride film 48