This thesis presents a study of the dielectric properties of perovskite La-Ti-O-N thin films for microwave applications. Thin films have been deposited by reactive RF sputtering from oxide or oxynitride targets. Depending on deposition conditions, and especially the plasma composition, different compositions have been obtained leading to a broad spectrum of dielectric properties. Oxynitride films show high dielectric constants that are associated with high dielectric losses. A limited tunability of 8 % under 16.7 kV/cm has been measured at low frequencies. Furthermore, the oxide thin films show low dielectric losses (~ 1 %) at 10 GHz but no agility. The composite combining results in an oxynitride/oxide bi-layer. That way, a tunability of about 15 % under 44 kV/cm can be reached while maintaining acceptable levels of dielectric loss.
