SiNx:H films have been deposited using two different ECR plasma sources attached to a similar deposition chamber, a Compact source and an AX4500 source both from Astex. The sources mainly differ in the discharge volume, 55 cm(3) and 936 cm(3), respectively. Microwave power and N-2/SiH4 gases now ratio have been varied to deposit the films. Deposition rate, infrared absorption spectra, refractive index (n), and optical band gap (E-g) of the films have been measured. Optical diagnosis spectra of the discharges have been recorded during the depositions. Different performances of the sources reflected in the film characteristics have been found. The properties of the films deposited using the Compact source correspond to films with compositions that range from Si-rich to near stoichiometric ones, while when using the AX4500 reactor, the film properties correspond to compositions close to the stoichiometric films or to N-rich ones. When changing from the Compact source to tile AX4500 reactor, the signal corresponding to N-2(+) ions and to the excited species, N-2(+) are higher in the AX 4500 than in the Compact one, the deposition rate being higher in tile AX 4500 source. The different performances of the sources have been attributed to the different discharge size and diffusion length, being optimal in the case of the AX4500 source.