Replacement gate work function material stacks are provided, which provides a work function about the energy level of the conduction band of silicon. After removal of a disposable gate stack, a gate dielectric layer is formed in a gate cavity. A metallic compound layer including a metal and a non-metal element is deposited directly on the gate dielectric layer. At least one barrier layer and a conductive material layer is deposited and planarized to fill the gate cavity. The metallic compound layer includes a material having a work function about 4.4 eV or less, and can include a material selected from tantalum carbide and a hafnium-silicon alloy. Thus, the metallic compound layer can provide a work function that enhances the performance of an n-type field effect transistor employing a silicon channel.