"hydrogen atom, NH.sub.2CH.sub.2CH.sub.2--(NHCH.sub.2CH.sub.2).sub.x--, an aliphatic alkyl group including at least one nitrogen atom, or a cyclo alkyl including at least one nitrogen atom, wherex is an integer from 0 to 10; and n is an integer from 3 to 20.The first tunneling oxide layer is formed of a material having a higher dielectric constant than the second tunneling oxide layer." . . . . .