The spectroscopic study of a-CNx thin films deposited by R.F. magnetron sputtering is reported. The bonding structure was determined using FTIR, Raman Scattering, NEXAFS and XPS results. The combination of the FTIR and Raman spectroscopy using the vibrational properties and the XPS and NEXAFS using the electronic properties of the materials is useful for a good description of the local structure in carbon nitride. The investigation is focused on the effect of the RF power and substrate temperature on the nitrogen surrounding in carbon nitride thin films. A good correlation is observed between the evolution of the π* electron states as calculated from NEXAFS, the evolution of the sp2 bonding of carbon observed in XPS, and the evolution of the electrical and optical properties of the films. These results combined with FTIR and Raman analysis and the elemental composition determined by nuclear microanalysis allow to follow the evolution of the local structure with the deposition conditions in a-CNx films.