Piezoelectric vibrator, piezoelectric oscillator, and piezoelectric vibrator manufacturing method having electrodes with different thicknesses

A method of manufacturing a piezoelectric vibrator, the method comprising:

• preparing a piezoelectric vibration element that includes:
• a piezoelectric blank having a first principal surface, a second principal surface opposing the first principal surface, and a vibration portion;
• a first excitation electrode on the first principal surface and within at least a part of the vibration portion of the piezoelectric blank;
• a second excitation electrode on the second principal surface and within at least a part of the vibration portion of the piezoelectric blank;
• and a second extended electrode on the second principal surface of the piezoelectric blank and electrically connected to the second excitation electrode;
• forming an insulation layer so as to cover the second excitation electrode and the second extended electrode;
• providing a first extended electrode on the first principal surface of the piezoelectric blank and which is electrically connected to the first excitation electrode;
• and
• removing a part of the insulation layer so as to form a hollow portion that defines a space with the second excitation electrode, wherein
• a thickness of the first extended electrode is larger than a thickness of the second extended electrode, and
• an end portion of the first extended electrode extends over the hollow portion in a plan view of the piezoelectric vibrator.