There is no mobile electrons in p-type neutral region (it is extremely low).
Electrons can appear in the depletion region due to thermal generation (electron excitation from the valence band, across band gap, into conduction band).
2. what region operates the thermal generation? (drain or source or ...)Thermal generation (s. above) is a rather slow process.
VGB > Vth is the definition for a conductive channel due to an inversion layer between source an drain.1. Is there an inversion layer between the Drain and Source terminal when VGB a little bigger than Vth?
Thermal generation/recombination occurs everywhere in a semiconductor. It constitutes the main part of leakage current. It increases exponentially with temperature.2. what region operates the thermal generation? (drain or source or ...)
Yes, and they get attracted to the SiO2/Si interface by the positive VGB (for NMOSFETs), there forming the inversion channel connecting drain & source.3. the inversion layer is composed of the electrons that from the thermal generation?