Piezoelectric resonator unit and method of manufacturing the same

A piezoelectric resonator unit comprising:

• a base member;
• a piezoelectric resonator having a piezoelectric element and a first excitation electrode and a second excitation electrode facing each other with the piezoelectric element interposed therebetween, the second excitation electrode facing the base member;
• a first conductive holding member and a second conductive holding member that mount the piezoelectric resonator on the base member and are respectively electrically connected to the first excitation electrode and the second excitation electrode;
• and
• a lid member joined to the base member such that the piezoelectric resonator is located between the lid member and the base member,
• wherein each of the first excitation electrode and the second excitation electrode include an underlying layer containing chromium as a main component thereof and a surface layer containing gold as a main component thereof,
• wherein an amount of the chromium diffused onto a surface of the surface layer is larger in the second excitation electrode than in the first excitation electrode, and
• Cr2O3 is on at least a part of the surface of the surface layer in the first excitation electrode and the second excitation electrode.