Patent ID: 7902588

Claim:
A nonvolatile semiconductor memory device comprising: a semiconductor region of a first conductive type; source and drain regions of a second conductive type; a channel region formed between the source and drain regions; a tunneling insulating film formed on the channel region; a floating gate electrode formed on the tunneling insulating film, the floating gate electrode including silicon; an inter-electrode insulating film formed on the floating gate electrode; and a control gate electrode formed on the inter-electrode insulating film, wherein an interface between the inter-electrode insulating film and the floating gate electrode is defined as a first interface, and an interface between the inter-electrode insulating film and the control gate electrode is defined as a second interface, wherein the inter-electrode insulating film includes one or more first elements, one or more second elements, and oxygen, and, wherein the first element is selected from rare earth elements, and the second element is selected from Al, Ti, Zr, Hf, Ta, Mg, Ca, Sr and Ba, wherein a composition ratio of the first element to the second element, which is defined as the number of atoms of the first element divided by that of the second element, is different between the first interface and the second interface, wherein the composition ratio of the first element to the second element in the inter-electrode insulating film in the vicinity of the second interface is equal to or less than 0.9, and wherein the composition ratio of the first element in the inter-electrode insulating film in the vicinity of the first interface is lower than that in the vicinity of the second interface.