The floating gate MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) has a fascinating history, playing a crucial role in the development of non-volatile memory technologies such as EEPROM (Electrically Erasable Programmable Read-Only Memory) and flash memory. I was introduced to transistors in Electronics school during my time in the USMC where I learned how to build, test and repair systems used to communicate, track and land aircraft. Who would of guessed that these little transistors would have such an impact on the world.
The MOSFET was first invented by Mohamed Atalla and Dawon Kahng at Bell Labs in the late 1950s. This revolutionary transistor design utilized a metal gate separated from the semiconductor channel by a thin insulating layer of silicon dioxide (SiO2). The MOSFET offered improved performance, lower power consumption, and greater integration capabilities compared to its predecessors.
The concept of the floating gate in MOSFETs was introduced by Dawon Kahng in 1967. Kahng’s idea involved adding a second insulated gate, isolated by an additional thin oxide layer, to the existing MOSFET structure. The key innovation was that the floating gate could be electrically isolated and store charge, creating a new mechanism for non-volatile memory storage.
In the 1970s, engineers at Intel, including Dov Frohman-Bentchkowsky, further developed the concept of the floating gate and introduced the Electrically Erasable Programmable Read-Only Memory (EEPROM). EEPROM allowed individual memory cells to be programmed and erased electrically, without the need for exposure to ultraviolet light or high voltages used in previous erasable PROM technologies.
The floating gate concept laid the foundation for the development of flash memory in the 1980s. Dr. Fujio Masuoka, a Toshiba engineer, is credited with inventing flash memory in 1980. Flash memory expanded on the EEPROM technology by introducing a grid-like structure of memory cells organized into blocks and sectors. This arrangement enabled faster erasing and programming of large chunks of memory, making flash memory more practical for mass storage applications.
The floating gate MOSFET and flash memory continued to evolve over the years, with advancements in cell scaling, multi-level cell (MLC) technology, and the introduction of NAND flash architecture. The shrinking of memory cell sizes and increased storage capacities fueled the widespread adoption of flash memory in various devices, including USB drives, solid-state drives (SSDs), smartphones, digital cameras, and many other consumer electronics.
Today, the floating gate MOSFET remains a critical component of non-volatile memory technologies. While newer memory technologies like NAND and NOR flash, as well as emerging technologies such as 3D NAND and resistive RAM (RRAM), are pushing the boundaries of memory capabilities, the fundamental concept of the floating gate in MOSFETs continues to be at the core of non-volatile memory and the basis of this site. I will explore past, current and new technologies and give my opinion on their effect on the industry.
