Abstract: A method of fabricating an integrated optical device and such a device, comprising a structure including at least one waveguiding element are presented. A basic structure is formed containing a substrate material carrying a buffer material layer coated with a core material layer of a higher refraction index as compared to that of the buffer layer. The at least one waveguiding element is defined in a guiding layer on top of the basic structure. The guiding layer is made of a material with a refractive index higher than the refractive index of the buffer layer and the core layer, and is chosen so as to minimize a height of the at least one waveguiding element and to provide effective guiding of light in the core layer.