Patent ID: 8889492

Claim:
A method of fabricating a multistate nonvolatile memory element, the method comprising: forming a first layer operable as a first variable resistance layer; forming a second layer operable as a second variable resistance layer over the first layer; and forming a third layer operable as a third variable resistance layer over the second layer; wherein the first layer is connected in series with the second layer and the second layer is connected in series with the third layer; wherein the first layer is configured to switch between a first low resistance state and a first high resistance state; wherein the second layer is configured to switch between a second low resistance state and a second high resistance state; wherein the third layer is configured to switch between a third low resistance state and a third high resistance state; wherein each of the first layer, the second layer, and the third layer comprises one of hafnium oxide, tantalum oxide, aluminum oxide, lanthanum oxide, yttrium oxide, dysprosium oxide, ytterbium oxide, lutetium oxide, lanthanum aluminum oxide, lanthanum lutetium oxide, or zirconium oxide; and wherein the multistate nonvolatile memory element has at least four different stable resistance states.