providing a basic structure including a substrate, and a field isolation film protruding from the substrate;

forming a first conductive film on the substrate and planarizing the first conductive film to form floating gates on opposite sides of the field isolation film;

subsequently performing a first etch process that reduces the thickness of the field isolation film to expose upper portions of the floating gates;

while the upper portions of the floating gates are exposed, performing a second etch process that is different from said first etch process, wherein said second etch process comprises knocking off upper edges of each of the floating gates, at which sidewalls of the floating gate intersect an upper surface thereof, such that at least upper portions of the sidewalls of each of the floating gates becomes sloped; and

subsequently forming a dielectric film and a second conductive film in sequence on the resultant structure.