Abstract: To provide a semiconductor memory device having an improved write efficiency because deterioration of a gate insulating film is suppressed. An element formation region is formed in a region of a semiconductor substrate sandwiched between element isolation regions. In the element isolation regions, a silicon oxide film is filled in a trench having a predetermined depth. An erase gate electrode is formed in the element isolation region while being buried in the silicon oxide film. Over the element formation region, floating gate electrodes are formed via a gate oxide film and control gate electrodes are formed over the floating gate electrodes via an ONO film. Two adjacent floating gate electrodes have therebetween an insulating film formed to cover the erase gate electrode.