30 Ångström thickness for EEPROM. According to NCR Corporation's patent application in 1980, SONOS structure required +25 volts and −25 volts for writing and erasing, respectively. It was improved to +12 V by PMOS-based MNOS (metal-nitride-oxide-semiconductor) structure. By the early 1980s, polysilicon NMOS-based structures were in use with operating voltages under 20 V. By the late 1980s and early 1990s PMOS SONOS structures were demonstrating program/erase voltages in the range of 5–12 volts. On the other hand, in 1980, Intel realized highly reliable EEPROM with double layered polysilicon structure, which is named FLOTOX, both for erase and write cycling endurance and for data retention term. SONOS has been in the past produced by Philips Semiconductors, Spansion, Qimonda and Saifun Semiconductors. Recent efforts In 2002, AMD and Fujitsu, formed as Spansion in 2003 and later merged with Cypress Semiconductor in 2014, developed a SONOS-like MirrorBit technology based on the license from Saifun Semiconductors, Ltd.'s NROM technology. As of 2011 Cypress Semiconductor developed SONOS memories for multiple processes, and started to sell them as IP to embed in other devices. UMC has already used SONOS since 2006 and has licensed Cypress for 40 nm and other nodes. Shanghai Huali Microelectronics Corporation (HLMC) has also announced to be producing Cypress SONOS at 40 nm and 55 nm. In 2006, Toshiba developed a new double tunneling layer technology with SONOS structure, which utilize Si9N10 silicon nitride. Toshiba also researches MONOS ("Metal-Oxide-Nitride-Oxide-Silicon") structure for their 20 nm node NAND gate type flash memories. Renesas Electronics uses MONOS structure in 40 nm node era. which is the result of collaboration with TSMC. While other companies still use FG (floating gate) structure. For example, GlobalFoundries use floating-gate-based split-gate SuperFlash ESF3 cell for their 40 nm products. Some new structure for FG (floating gate) type flash memories are still intensively studied. In 2016, GlobalFoundries developed FG-based 2.5V Embedded flash macro. In 2017, Fujitsu announced to license FG-based ESF3/FLOTOX structure, which is originally developed by Intel in 1980, from Silicon Storage Technology for their embedded non-volatile memory solutions. As of 2016, Intel-Micron group have disclosed that they stayed traditional FG technology in their 3-dimensional NAND flash memory. They also use FG technology for 16 nm planar NAND flash. See also Polycrystalline silicon Silicon dioxide Silicon nitride Silicon MOSFET Charge trap flash Floating-gate MOSFET EEPROM Flash memory References External links Gutmann (2001) papaer: "Data Remanence in Semiconductor Devices" USENIX Computer