To provide a thin-film capacitor which is compact and large in capacitance, and is highly reliable and can match easily a production process for an MMIC(monolithic microwave integrated circuit), etc.

This production method is used to form a thin-film capacitor which is formed of a substrate, a lower electrode formed thereon, a dielectric thin film formed thereon, an upper electrode formed thereon, and the dielectric thin-film contains at least Sr, Ti and O and is formed at 350°C or lower through a plasma CVD. In addition, it is preferably made of SrTiO3-based perovskite type compound in consideration of permittivity, etc. Further, it is formed through diode parallel plate plasma CVD, and the high-frequency output at that time is preferably 2 W/cm2 or more and 8 W/cm2 or less.