Floating Gate memory

A floating gate MOSFET is an example of a memory cell. The memory cell looks the same as the ordinary MOSFET transistor but with an extra gate.

That extra gate is called the floating gate. The floating gate is between the normal gate and the bottom where the electron pathway is formed. It is completely surrounded by insulating material. Due to this insulating material, the floating gate is completely electrically separated from the rest of the memory cell.

You can trap the electrons in the floating gate by applying very high voltages on the normal gate, thus attracting the electrons so strongly they will “jump” across the insulating layer into the floating gate, getting trapped there.

If electrons are trapped into the floating gate, they will stay there. So the floating gate is the memory element in which you can lock up electrons.