Semiconductor device and method of manufacturing the same

A semiconductor device and a manufacturing method thereof for preventing gate electrode degradation and gate current leakage. The semiconductor device includes a gate insulating layer including an H-k (high dielectric) material on a semiconductor substrate, a barrier metal layer including a metal alloy on the gate insulating layer, and a gate electrode layer formed on the barrier metal layer. Illustratively, the barrier metal layer includes at least one of TaAlN (tantalum aluminum nitride) or TiAlN (titanium aluminum nitride). The barrier metal layer can include an oxidation-resistant material so that oxidation of the barrier metal layer is prevented during a subsequent annealing of the semiconductor device in an oxygen atmosphere. Thus, degradation of a gate electrode is prevented, and gate current leakage due to degradation of the gate electrode is prevented.