PURPOSE: To increase the capacitance variation rate by forming a piezoelectric bias part integrally on the outside of of a capacitor part, forming first and second electrodes on both major surfaces of a piezoelectric material layer at the piezoelectric bias part, and then applying a bias voltage between both electrodes.

CONSTITUTION: A capacitor part 22 comprises a rectangular prism sintered dielectric ceramic 24 in which inner electrodes 25 to 28 are stacked through dielectric layers. A piezoelectric bias part 23 integrated with the capacitor part 22 on the outside comprises a layer 32 composed only of piezoelectric ceramic and an electrode 33 formed on the outer surface of the layer 32 where the electrodes 31, 33 are facing each other through the layer 32. When a voltage is applied between the electrodes 31, 33, the layer 32 expands and contracts to apply a strain to the sintered ceramic 24 and thereby the dielectric layer between the electrodes 25 to 28 is distorted thus varying the capacitance. The capacitance can be varied continuously by varying the bias voltage.