Methods of forming a microelectronic device can include providing a gate dielectric layer on a channel region of a semiconductor substrate wherein the gate dielectric layer is a high-k dielectric material. A gate electrode barrier layer can be provided on the gate dielectric layer opposite the channel region of the semiconductor substrate, and a gate electrode metal layer can be provided on the gate electrode barrier layer opposite the channel region of the semiconductor substrate. The gate electrode barrier layer and the gate electrode metal layer can be formed of different materials. Moreover, the gate electrode metal layer can include a first material and the gate electrode barrier layer can include a second material, and the first material can have a lower electrical resistivity than the second material.