Patent ID: 8254175

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, 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 comprises: a first region which is formed on the surface of the semiconductor region and contains oxygen and at least one of silicon and germanium, as main components; a second region which contains nitrogen and at least one of silicon and germanium, as main components; a third region which is formed on a back surface of the charge-storage insulating film and contains oxygen and at least one of silicon and germanium, as main components; and a fourth region which is an insulating region, between the second region and the third region, a nitrogen concentration in the fourth region being lower than a nitrogen concentration in the second region, and an oxygen concentration in the fourth region being lower than an oxygen concentration in the third region, the second region is formed between the first region and the third region.