An Electrically Erasable Programmable Read-Only Memory (EEPROM) is a type of semiconductor storage device that employs an electrical means for erasure. The memory cells consist of FLOating-gate Tunneling OXide (FLOTOX) technology to achieve this. A typical cell, also known as a FLOTOX Transistor, consists of a pair of polysilicon gates, where one gate provides the control function whilst the other remains floating. The principle employs electron tunnelling through an extremely thin layer of silicon dioxide and programming involves the transfer of electrons through this oxide between the floating gate and substrate.

History

A major disadvantage of the earlier EPROM technology was that it required removal from its socket during erasing and programming, because erasing required additional UV light source paraphernalia. The invention of electrically erasable PROM (EEPROM) occurred in approximately 1980 to overcome this limitation, and one of the earliest chips to become available was the famous Intel 2816, which was a 16K memory chip. This technology gave the user ability to reprogram the chip whilst keeping it in its socket and the user could chose to erase the entire memory or parts of it up to bit level.