Electrical resistivity measurements vs. frequency were performed on two molybdenum coatings grown by RF magnetron sputtering technique on a sapphire substrate at room temperature and annealed at different temperatures. Data show that the surface resistivity changes with the annealing while the conductivity of these Mo coatings can be almost doubled. In agreement with other researches, the results confirm that Mo coatings with an electrical conductivity comparable to that of copper can be obtained optimizing the thickness and the post-deposition annealing process. Morphological and structural investigations on Mo coatings were performed before and after annealing by synchrotron radiation X-ray diffraction and X-ray absorption spectroscopy to identify the chemical status of Mo, to probe the presence of different oxides and to control the multiphase nature of these metallic films.