A semiconductor device includes an interelectrode insulating film formed between a charge storage layer and a control electrode layer. The interelectrode insulating film is formed in a first region above an upper surface of an element isolation insulating film, a second region along a sidewall of the charge storage layer, and a third region above an upper surface of the charge storage layer. The interelectrode insulating film includes a first stack including a first silicon nitride film or a high dielectric constant film interposed between a first and a second silicon oxide film or a second stack including a second high dielectric constant film and a third silicon oxide film, and a second silicon nitride film formed between the control electrode layer and the first or the second stack. The second silicon nitride film is relatively thinner in the third region than in the first region.