Floating-gate transistor

Floating-gate transistor Floating-gate transistor is one of varieties of the MOS field-effect transistor. The gate of the transistor is placed deep in the dielectric in some distance from all the transistor contacts, which does not allow electrons with little energy get to it. The control gate is located next to it. If voltage is applied to it, many electrons obtain the energy so high that they can pass through the dielectric and settle on the floating gate, turning its charge from neutral into negative. Electrons that have got onto the floating gate can stay there over dozens of years, and their number will not reduce unless voltage is applied to the transistor. If the voltage applied to the floating gate is of the opposite sign, the electrons start running off it, discharging it. In this case the floating gate performs the same function as that of the capacitor in DRAM memory: it stores encoded data. Such transistors are used in various non-volatile memory devices: flash memory or EEPROM.