Floating-gate MOSFET

Since the FG is surrounded by highly resistive material, the charge contained in it remains unchanged for long periods[1] of time, typically longer than 10 years in modern devices.

The MOSFET was invented at Bell Labs between 1955 and 1960, after Frosch and Derick discovered surface passivation and used their discovery to create the first planar transistors.

Modern FGMOS used in flash memories are based on Fowler-Nordheim tunnelling EEPROM gates, which was invented by Bernward and patented by Siemens in 1974[12] and further improved by Israeli-American Eliyahou Harari at Hughes Aircraft Company and George Perlegos and others at Intel.

If it is possible to determine the voltage at the FG of an FGMOS device, it is then possible to express its drain to source current using standard MOS transistor models.

A transient analysis is then run with the supply voltages set to their final values, letting the outputs evolve normally.

Examples of application for this regime are single transistor adders, DACs, multipliers and logic functions, and variable threshold inverters.

Using the FGMOS as a programmable charge element, it is commonly used for non-volatile storage such as flash, EPROM and EEPROM memory.

In this context, floating-gate MOSFETs are useful because of their ability to store an electrical charge for extended periods of time without a connection to a power supply.