PURPOSE: To eliminate the need for a stationary container and a holding member and almost remove external influence by converging thickness-shear oscillation energy to a piezoelectric area at a center part, and reducing the oscillation displacement of the surface of a piezoelectric element extremely.

CONSTITUTION: Driving electrodes 4 and 5 are formed on surfaces 2a and 2b of a crystal piece 2 by vacuum-depositing metal or other methods. A lead-out electrode 4a from one driving electrode 4 is extended to the end part of the other main surface 2b. A crystal vibrator 1 is fixed directly to a substrate not shown in figure with an adhesive, etc., and the lead-out electrode 4a connects with a wiring pattern and the driving electrode 4. When an electric field is impressed to the driving electrodes 4 and 5, the crystal vibrator 1 enters thickness- shear oscillation. The displacement of the thickness-shear oscillation is maximum near interfaces between the piezoelectric area 2c and nonpiezoelectric areas 3a and 3a. Then, the oscillation displacement attenuates gradually in the nonpiezoelectric areas 3a and 3a and becomes extremely smaller on the surfaces 2a and 2b almost to zero.