Working principle of floating gate tunneling oxide
In general, electron tunneling is based on the quantum mechanical concept that the "wave function" of the electron &mdash; a function that describes the probability of finding the electron in any particular position &mdash; does not end abruptly at the surface of a conductor (or semiconductor), but can extend all of the way through an otherwise impassable barrier.

The tunnelling current can be controlled by varying the electrical potentials on either side of the floating gate, which changes the electric fields across the gate and its surrounding oxide barriers, which in turn affects the wave functions of the nearby conduction-band electrons.

If you're asking about the specific electrode structures and timing protocols used in a particular device &mdash; generally, that information is considered very proprietary to each manufacturer and is not publicly available.