A method of forming a transistor device includes forming an interfacial layer on a semiconductor substrate, corresponding to a region between formed doped source and drain regions in the substrate; forming a high dielectric constant (high-k) layer on the interfacial layer, the high-k layer having a dielectric constant greater than about 7.5; forming a doped metal layer on the high-k layer; performing a thermal process so as to cause the doped metal layer to scavenge oxygen atoms diffused from the interfacial layer such that a final thickness of the interfacial layer is less than about 5 angstroms (Å); and forming a metal gate material over the high-k dielectric layer.