The aim of this paper is the study of ruthenium dioxide (RuO2) films, grown on low-stress silicon nitride on silicon (SiNx/Si), in order to develop thermal micro-sensors based on pyroelectric effect. The active part of these micro-sensors is constituted by a new arrangement : lithium tantalate (LiTaO3)/RuO2/SiNx/Si. Radio-frequency (RF) sputtering is employed to deposit RuO2 on SiNx/Si substrate. Morphology, crystallinity and resistivity of RuO2 are studied as function of growth parameters. Next, RF magnetron sputtering was used to deposit LiTaO3 on this electrode. Morphology studies, pyroelectric effect and dielectric parameters obtained, indicate that RuO2 material is a suitable candidate as back electrode for LiTaO3 thin films. (c) 2006 Elsevier B.V. All rights reserved.