Reducing the inversion oxide thickness of a high-k stack fabricated on high mobility semiconductor material

A method of forming a semiconductor structure comprising:

• forming a high mobility semiconductor layer over a semiconductor substrate, wherein the high mobility semiconductor layer comprises one of Ge, GaAs, InGaAs, InP, InSb, InAs, AlGaAs, and InALAs;
• forming an interfacial oxide layer over the high mobility semiconductor layer;
• forming a high dielectric constant (high-k) dielectric layer over the interfacial oxide layer;
• forming a stack over the high-k dielectric layer, wherein the stack comprises a lower metal layer formed on the high-k layer, a scavenging metal layer comprising a scavenging metal formed on the lower metal layer, and an upper metal layer formed on the scavenging metal layer, wherein the scavenging metal layer consists one of B, C, Cb, Cr, Cs, Ga, In, Li, Mn, Na, P, Si, Ta, Th, V, and Zn, and wherein the scavenging metal layer is selected based on at least the high mobility semiconductor layer,
• wherein a Gibbs free energy change of a chemical reaction, in which an atom constituting the high mobility semiconductor layer that directly contacts the interfacial oxide layer combines with a metal oxide material comprising the scavenging metal and oxygen to form the scavenging metal in elemental form and oxide of the atom constituting the high mobility semiconductor layer that directly contacts the interfacial oxide layer, is positive;
• and
• forming a gate electrode and a gate dielectric, wherein the gate electrode is formed by patterning the stack, and wherein the gate dielectric includes a portion of the high-k dielectric layer.