Resistive random-access memory (ReRAM or RRAM) is a type of non-volatile (NV) random-access (RAM) computer memory that works by changing the resistance across a dielectric solid-state material, often referred to as a memristor. ReRAM bears some similarities to conductive-bridging RAM (CBRAM) and phase-change memory (PCM). CBRAM involves one electrode providing ions that dissolve readily in an electrolyte material, while PCM involves generating sufficient Joule heating to effect amorphous-to-crystalline or crystalline-to-amorphous phase changes. By contrast, ReRAM involves generating defects in a thin oxide layer, known as oxygen vacancies (oxide bond locations where the oxygen has been removed), which can subsequently charge and drift under an electric field. The motion of oxygen ions and vacancies in the oxide would be analogous to the motion of electrons and holes in a semiconductor. Although ReRAM was initially seen as a replacement technology for flash memory, the cost and performance benefits of ReRAM have not been enough for companies to proceed with the replacement. Apparently, a broad range of materials can be used for ReRAM. However, the discovery that the popular high-κ gate dielectric HfO2 can be used as a low-voltage ReRAM has encouraged researchers to investigate more possibilities. RRAM® is the registered trademark name of Sharp Corporation, a Japanese electronic components manufacturer, in some countries, including members of the European Union. History In the early 2000s, ReRAMs were under development by a number of companies, some of which filed patent applications claiming various implementations of this technology. ReRAM has entered commercialization on an initially limited KB-capacity scale. In February 2012, Rambus bought a ReRAM company called Unity Semiconductor for $35 million. Panasonic launched an ReRAM evaluation kit in May 2012, based on a tantalum oxide 1T1R (1 transistor – 1 resistor) memory cell architecture. In 2013, Crossbar introduced an ReRAM prototype as a chip about the size of a postage stamp that could store 1 TB of data. In August 2013, the company claimed that large-scale production of their ReRAM chips was scheduled for 2015. The memory structure (Ag/a-Si/Si) closely resembles a silver-based CBRAM. Also in 2013, Hewlett-Packard demonstrated a memristor-based ReRAM wafer, and predicted that 100 TB SSDs based on the technology could be available in 2018 with 1.5 PB capacities available in 2020, just in time for the stop in growth of NAND flash capacities. Different forms of ReRAM have been disclosed, based on different dielectric materials, spanning from perovskites to transition