ABSTRACT
This chapter reviews the basic principles of operation of the U-shaped Gate Trench metal oxide semiconductor field effect transistor (UMOSFET) structure. The transfer characteristics of the MOSFETs were obtained by measuring the drain current as the gate-source voltage was swept for a fixed drain-source voltage. The behavior of the shielded structure with respect to other blocking voltages is similar to that provided for the conventional UMOSFET structure. The shielded UMOSFET power MOSFET operates in the forward blocking mode when the gate electrode is shorted to the source by the external gate drive circuit. The threshold voltage of the UMOSFET structure is determined by the doping concentration of the P-well region along the sidewalls of the trench region. Both conventional UMOSFET and shielded UMOSFETs are inversion-channel devices and their on-resistances are greatly affected by the resistance of the metal oxide semiconductor channel.
