A capacitor has a lower electrode, a dielectric thin film, an upper electrode, and an insulation cover layer formed on an insulation substrate made of an organic film or a ceramic material, and through holes formed at positions corresponding to input and output pads of a semiconductor element or to input and output terminals of a semiconductor package, with electrodes for connection to input and output pads of a semiconductor element or to input and output terminals of a semiconductor package provided within through holes. In a method for mounting the capacitor, the capacitor is interposed between a flip-chip connected semiconductor element and a mounting substrate.