A semiconductor device including a semiconductor substrate; a first gate insulating film formed on the semiconductor substrate; a first gate electrode layer formed on the first gate insulating film; an element isolation insulating film formed so as to isolate a plurality of the first gate electrode layers; a second gate insulating film layer formed so as to cover upper surfaces of the plurality of first gate electrode layers and the element isolation insulating films; and a second gate electrode layer formed on the second gate insulating film layer; and the second gate insulating film layer includes a NONON stacked film structure and a nitride film layer contacting the first gate electrode layer and constituting a lowermost layer of the NONON stack film structure is separated at a portion interposing the plurality of neighboring first gate electrode layers.