Semiconductor device and method of manufacturing the same

A method of manufacturing a semiconductor device, comprising:

• forming a first gate insulating film and a first conductive layer on a semiconductor substrate;
• separating the first conductive layer by forming an element isolation trench in the first conductive layer, the first gate insulating film and the semiconductor substrate;
• forming an element isolation insulating film in the element isolation trench so as to provide a first exposed surface on at least a portion of the first conductive layer and a second exposed surface on the element isolation insulating film;
• selectively forming a nitride film layer constituting a lowermost layer of a second gate insulating film layer on the exposed surface of the first conductive layer except the second exposed surface while selectively excluding formation of said nitride film layer on said second exposed surface except for outer edges of said second exposed surface;
• and
• forming an oxide film layer constituting the second gate insulating film layer on the nitride film layer and the element isolation insulating film.

A method of manufacturing a semiconductor device including a semiconductor substrate including a pair of active areas, each active area having a first upper surface, respectively, an element isolation insulating film separating the active areas, the element isolation insulating film including a second upper surface being higher than the first upper surface, gate insulating films formed on the active areas, and a plurality of floating gate electrodes formed on the gate insulating films, each floating gate electrode including a third upper surface being higher than the second upper surface of the element isolation insulating film relative to the first upper surface of the active area, a lower side surface facing a side surface of the element isolation insulating film and an upper side surface located above the lower side surface without facing the side surface of the element isolation insulating film, comprising:

• forming an inter-gate insulating film on the floating gate electrodes and the element isolation insulating film, including
• executing a first radical nitridation treatment to the third upper and upper side surfaces of the floating gate electrodes and the second upper surface of the element isolation insulating film by a first pressure so as to selectively form a first silicon nitride film having a first thickness on the third upper and upper side surfaces of the floating gate electrodes without forming the first silicon nitride film on the second upper surface of the element isolation insulating film,
• forming a first silicon oxide film on the first silicon nitride film and the second upper surface of the element isolation insulating film,
• forming a second silicon nitride film on the first silicon oxide film,
• forming a second silicon oxide film on the second silicon nitride film, and
• executing a second radical nitridation treatment to the second silicon oxide film by a second pressure being less than the first pressure so that a third silicon nitride film is formed on the second silicon oxide film, and
• forming a control gate electrode on the third silicon nitride film of the inter-gate insulating film.