In this work, we report on the optimization of all process steps for the fabrication of optical waveguides with high index contrast by using as core and cladding layers silicon oxynitnde films deposited by plasma enhanced chemical vapor deposition at low temperatures. The main advantage of using this material, besides allowing the integration of optical and microelectronic devices, is the possibility of controlling accurately the refractive index over a wide range (n = 1.46-2) allowing in this way a precise control of the index contrast and favoring a high integration density and relatively small dimensions in optical integrated circuits. © 2004 Elsevier B.V. All rights reserved.