Magnesium boride films are synthesized from Mg(BH4)2 by CVD. A new synthesis of the precursor is developed. Deposition time of the samples is varied to study its influence on film composition. The films are analyzed by means of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The contributions of various chemical species (boride and oxides) in the depth profiles, carried out using Ar ion sputtering combined with cyclic XPS measurements, are separated by peak-fitting analysis of photoelectron B1s and Auger MgKLL spectra. The samples are composed of MgBx film covered by an overlayer of magnesium and boron oxides.