Abstract: A semiconductor device is disclosed, which comprises source and drain regions formed in a spaced-apart relation to each other on an isolated semiconductor substrate surface, a first conductive layer formed over a channel region between the source and drain regions via a gate insulating film and serving as a floating gate electrode, a two-layer insulating layer formed on the first conductive layer and consisting of a silicon oxynitride film and a silicon oxide film, and a second conductive layer formed on the two-layer insulating layer and serving as a control gate electrode. In the semiconductor device of this structure, the silicon oxynitride film traps fewer electrons, and electrons are infrequently trapped at the time of data erasing, so that data-erasing characteristics can be improved.