Patent ID: 8530876

Claim:
A semiconductor memory device comprising: a substrate; a lower electrode on the substrate; a variable resistance film on the lower electrode, the variable resistance film storing data in the form of an electrically programmable resistance; and an upper electrode on the variable resistance film, the variable resistance film comprising: a first film on a side of at least one of the upper electrode and the lower electrode, the first film containing a metal; and a second film between the first film and the other electrode, the second film containing the metal and oxygen; and a third film between the second film and the other electrode, the third film containing the metal, wherein a composition ratio [O]/[Me] of oxygen to the metal in the second film is lower than a stoichiometric ratio and higher than a composition ratio [O]/[Me] in the first film, the composition ratio [O]/[Me] changes between the first film and the second film, a composition ratio [O]/[Me] in the third film is lower than that in the second film, and the composition ratio [O]/[Me] changes between the third film and the second film.