PURPOSE: To prevent a ceramic substrate from being cracked due to an advance of a minute crack existing internally in the ceramic substrate by forming a thin film consisting of an inorganic material on at least one main face of the ceramic substrate.

CONSTITUTION: A piezoelectric resonator 11 is provided with a piezoelectric resonance element 10 in its inside, and in the part in which resonance electrodes 6, 7 are formed in the piezoelectric resonance element 10, voids 12, 13 for obstructing no vibration of the resonance electrodes 6, 7 are formed. Also, in a mother ceramic substrate, thin films 2, 3 consisting of ZnO are formed in advance by sputtering, and in the piezoelectric resonator 11 with a lead obtained finally, as well, the thin films 2, 3 are left. Accordingly, even if a physical shock is given in the manufacturing process, an advance and spread of a minute crack existing internally in the ceramic substrate are suppressed due to existence of the thin films 2, 3. Also, even if a physical shock is given to the obtained piezoelectric resonator 11, spread of the minute crack existing internally in the ceramic substrate is suppressed by an action of the thin films 2, 3 in the same way.