A high-frequency circuit device serving as a resonator includes a substrate and an electrode film which is formed on the surface of the substrate and which includes a conductive film and a dielectric film. The conductive film is formed around the substrate such that both ends of the conductive film overlap each other when viewed in a predetermined cross-section of the substrate, and the dielectric film is inserted between both ends of the conductive film. Accordingly, a self-capacitance portion is formed at the overlapped portion of the conductive film, electric-field energy is accumulated therein, and magnetic-field energy is accumulated inside the substrate. With this step impedance structure, the entire high-frequency circuit device can be miniaturized.