A semiconductor device includes a semiconductor substrate, a gate insulating film formed on the substrate, a first gate electrode formed on the gate insulating film, source and drain regions formed in the substrate so as to sandwich the first gate electrode, an intergate insulating film formed on the first gate electrode and including an opening, a second gate electrode formed on the intergate insulating film and electrically connected to the first gate electrode through the opening, and a boost electrode formed on the intergate insulating film and electrically isolated from the first gate electrode and the second gate electrode.