Patent ID: 8253189

Claim:
A semiconductor device comprising: a semiconductor region; a tunnel insulating film formed on a surface of the semiconductor region; a charge-storage insulating film formed on a surface of the tunnel insulating film and containing silicon and nitrogen; a block insulating film formed on a surface of the charge-storage insulating film; and a control gate electrode formed on a surface of the block insulating film, wherein the tunnel insulating film has a first insulating film formed on the surface of the semiconductor region and containing silicon and oxygen, a second insulating film formed on a surface of the first insulating film, and a third insulating film formed on a surface of the second insulating film and containing silicon and oxygen, the second insulating film contains silicon, nitrogen, and oxygen, and has a higher oxygen concentration than the charge-storage insulating film, and the oxygen in a central portion of the second insulating film has a higher concentration than the oxygen in a vicinity of an interface between the first insulating film and the second insulating film and the oxygen in a vicinity of an interface between the second insulating film and the third insulating film.