In this work we present results of Si/SiO2/SiON/SiO2 waveguides fabricated by means of ECR-PECVD. In order to change refraction index and simultaneously to reduce losses related with hydrogen, we have used N-2 as precursor gas for controlling the nitrogen to oxygen relation present in the samples. The composition of the samples were carefully controlled by RBS and ERDA analysis. The refractive index and thickness were measured by using a prisma coupler method at a wavelength of 632.8 nm.