Semiconductor memory device and method of manufacturing the same

摘要

A gate oxide film is formed on a surface of a semiconductor substrate. A tunnel insulating film having a thickness smaller than that of the gate insulating film is formed in a portion thereof corresponding to a tunnel region. A first silicon film having a low impurity concentration is formed on the gate insulating film. A second silicon film having an impurity concentration higher than that of the first silicon film is formed on the first silicon film so as to be connected thereto. A third silicon film is formed on the second silicon film through an insulating film. The second and third silicon films are formed into floating and control gates, respectively, thereby forming a semiconductor memory device.