Dual metal gate electrode for reducing threshold voltage

Abstract

A gate conductor material stack including, from bottom to top, of a first metallic nitride, a second metallic nitride, and a conductive material portion is employed for a transistor in combination with a gate dielectric including a high dielectric constant (high-k) dielectric material. The second metallic nitride includes a nitride of an aluminum-containing metallic alloy of at least two elemental metals, and can be selected from TaAlN, TiAlN, and WAlN. The second metallic nitride can provide a function of oxygen scavenging from the high-k gate dielectric and/or prevent diffusion of atoms from the conductive material portion. The gate conductor material stack can enable a reduced inversion thickness and/or a reduced magnitude for a linear threshold voltage for p-type field effect transistors compared with a gate electrode employing a single metallic material.