Patent ID: 8426909

Claim:
A nonvolatile semiconductor memory device comprising: a semiconductor region; a first insulating film on the semiconductor region; a charge storage layer on the first insulating film; a second insulating film on the charge storage layer; and a control gate electrode on the second insulating film, wherein the second insulating film includes a bottom layer (A) in contact with the charge storage layer, a top layer (C) in contact with the control gate electrode, and a middle layer (B) between the bottom layer (A) and the top layer (C), the middle layer (B) comprises (SiO 2 ) x (Si 3 N 4 ) 1-x (0.75≦x≦1), the bottom layer (A) comprises one of Al-oxide, Al-oxynitride, Al-silicate, Al-nitride-silicate, Hf-oxide, and Al—Hf-oxide, and the top layer (C) comprises one of Al-oxide, Al-oxynitride, Al-silicate, Al-nitride-silicate, and Si-nitride.