A semiconductor device includes a semiconductor substrate having a plurality of element regions and a plurality of element isolation regions in a first direction, a plurality of floating gate electrodes formed via a gate insulating film on the respective element regions, an intergate insulating film formed on the floating gate electrodes, a plurality of control gate electrodes formed on the intergate insulating film so as to extend over the adjacent floating gate electrodes, and an element isolation insulating film formed in the element isolation region and having an upper end located higher than the upper surface of the gate insulating film, the element isolation insulating film including a part formed between the control gate electrodes so that the central sidewall of the element isolation insulating film is located lower than the end of the sidewall of the element isolation insulating film.