A thin film device includes a thin film element disposed on a surface of a substrate for high voltage formed of a material having an electric resistivity in the range of 10.sup.8 .OMEGA.cm to 10.sup.10 .OMEGA.cm, with an adhesive layer in between. The substrate for high voltage is a sintered body containing Al.sub.2O.sub.3, TiC, and MgO in a predetermined weight ratio. Therefore, if electric charges are generated in the thin film element, the electric charges are, while they are not accumulated in large amounts, gradually shifted via the adhesive layer to the substrate for high voltage, so that the generation of ESD can be suppressed. On the other hand, even when mounted on a lead frame, a sufficient dielectric breakdown voltage can be ensured. This provides a thin film device that is less susceptible to damage due to ESD, and has superior withstand voltage characteristic to permit a stable operation.