Patent ID: 7875925

Claim:
A nonvolatile semiconductor memory device comprising: a source region and a drain region spaced from each other in a surface of a semiconductor layer; a tunnel insulating film provided on the semiconductor layer between the source region and the drain region; a charge storage film provided on the tunnel insulating film; a block insulating film provided on the charge storage film and made of (Rm 1−x Ln x ) 2−y Al y O 3+δ , where Ln is one or more selected from Pr, Tb, Ce, Yb, Eu, and Sm, Rm is one or more selected from La, Nd, Gd, Dy, Ho, Er, Tm, Lu, Y, and Sc, 0<x<0.167 (but 0<x<0.333 if Ln is Pr, and 0<x<0.292 if Ln is Tb), 0.95≦y≦1.20, and 0≦δ≦x(2−y)/2 (but −x(2−y)/2≦δ≦0 if Ln is Yb, Eu, and Sm, 0≦δ≦x(2−y)/3 if Ln is Pr, and 0≦δ≦3x(2−y)/14 if Ln is Tb); and a control gate electrode provided on the block insulating film.