Abstract: Low and high impedance thickness mode vibration portions are integrally laminated. Each vibrator portion comprises electrode layers between which a piezoelectric layer polarized in the direction of thickness is interposed. In each vibrator portion, every other electrode layer is connected to respective common external terminals. These common external terminals are of either four-terminal construction consisting two pairs, one pair for the low impedance mode vibrator portion and the other pair for the high impedance thickness mode vibrator portion, or three-terminal construction in which one of each pair are united together into a common terminal. Difference between the impedances is set on difference in the number of electrode layers and/or on difference in dielectric constant between the piezoelectric layers.