Multi-state ferroelectric-RAM with stacked capacitors

Abstract

A memory device includes a substrate and vertically stacked ferroelectric capacitors formed on the substrate. A first ferroelectric capacitor has a different capacitive output than a second ferroelectric capacitor when a constant voltage is applied. First and second electrodes are in electrical contact with the vertically stacked ferroelectric capacitors. In some instances, a first capacitor plate in the first ferroelectric capacitor and a second capacitor plate in the second ferroelectric capacitor have different thicknesses. The different thicknesses allow the capacitive output for each capacitor to produce different electric field outputs. Accordingly, a combination of different output signals can be produced based on different threshold voltage levels for each capacitor contributing to the output.

Dependencies are inferred from the claim text.