Impedance matching device

An impedance matching device includes a variable capacitor constituted by a non-linear dielectric thin film and an upper electrode disposed on a lower electrode formed on a substrate. The non-linear dielectric thin film is formed by a deposition, screen-printing, electroplating, or other technique, and changes its relative dielectric constant according to applied voltage. Therefore, the capacity of the variable capacitor is controlled and the impedance is matched, by simply controlling the applied voltage across the non-linear dielectric thin film. Consequently, the arrangement makes it possible to cut down the impedance matching device in size and cost, compared to an arrangement incorporating a capacitor and a coil for adjustment, effects a much simpler matching operation, and facilitates a manufacturing process.