the gate electrode of a metal oxide semiconductor field effect transistor comprises a source side gate electrode and a drain side gate electrode that abut each other near the middle of the channel . in one embodiment , the source side gate electrode comprises a silicon oxide based gate dielectric and the drain side gate electrode comprises a high - k gate dielectric . the source side gate electrode provides high carrier mobility , while the drain side gate electrode provides good short channel effect and reduced gate leakage . in another embodiment , the source gate electrode and drain gate electrode comprises different high - k gate dielectric stacks and different gate conductor materials , wherein the source side gate electrode has a first work function a quarter band gap away from a band gap edge and the drain side gate electrode has a second work function near the band gap edge .