US Patent 9595668 Self-rectifying RRAM element

The disclosed technology generally relates to semiconductor devices and more particularly to memory devices having a resistance switching element, and to methods of operating such memory devices. In one aspect, a memory cell includes a first electrode and a second electrode formed of one of a metallic material or a semiconducting material. The memory cell additionally includes a resistance switching element formed between the first electrode and the second electrode. The memory cell additionally includes a tunnel rectifier formed between the resistance-switching element and the first electrode. The tunnel rectifier includes a multi-layer tunnel stack comprising at least two dielectric layers each having a dielectric constant (ki), a conduction band offset (Φi), and a thickness, wherein one of the dielectric layers has a higher dielectric constant, a lower conduction band offset and a higher thickness compared to any other dielectric layer of the multi-layer tunnel stack.