Methods for forming a semiconductor device structure are provided. The methods may include forming a molybdenum nitride film on a substrate by atomic layer deposition by contacting the substrate with a first vapor phase reactant comprising a molybdenum halide precursor, contacting the substrate with a second vapor phase reactant comprise a nitrogen precursor, and contacting the substrate with a third vapor phase reactant comprising a reducing precursor. The methods provided may also include forming a gate electrode structure comprising the molybdenum nitride film, the gate electrode structure having an effective work function greater than approximately 5.0 eV. Semiconductor device structures including molybdenum nitride films are also provided.