Patent ID: 8658997

Claim:
A multistate nonvolatile memory element comprising: a first layer operable as a first variable resistance layer, the first layer configured to switch between a first low resistance state and a first high resistive state; a second layer operable as a second variable resistance layer, the second layer connected in series with the first layer, the second layer configured to switch between a second low resistance state and a second high resistance state; a third layer operable as a third variable resistance layer, the third layer connected in series with the first layer and the second layer, and the third layer configured to switch between a third low resistance state and a third high resistance state; and wherein each of the first layer, the second layer and the third layer comprises a first chemical element and a second chemical element, and wherein a ratio of the first chemical element to the second chemical element is different in each of the first layer, the second layer and the third layer, and wherein the multistate nonvolatile memory element has at least four different stable resistive states.