Methods of forming group III piezoelectric thin films via removal of portions of first sputtered material

A method of forming an acoustic resonator device, the method comprising:

• sputtering onto a first surface of a growth substrate to provide a piezoelectric thin film comprising AlN, AlScN, AlCrN, HfMgAlN, or ZrMgAlN on the first surface of the growth substrate;
• forming a first electrode on the piezoelectric thin film;
• forming a multilayer mirror or a reflector structure on the first electrode;
• forming a support layer on the multilayer mirror or reflector structure;
• coupling a bond substrate to the support layer;
• processing a second surface of the growth substrate that is opposite the first surface of the growth substrate to provide an exposed surface of the piezoelectric thin film from beneath the second surface of the growth substrate, wherein the exposed surface of the piezoelectric thin film comprises a first crystalline quality portion of the piezoelectric thin film;
• removing a portion of the exposed surface of the piezoelectric thin film to access a second crystalline quality portion of the piezoelectric thin film that is covered by the first crystalline quality portion of the piezoelectric thin film, wherein the second crystalline quality portion of the piezoelectric thin film has a higher quality than the first crystalline quality portion of the piezoelectric thin film;
• processing a surface of the second crystalline quality portion of the piezoelectric thin film to form a via that passes through the second crystalline quality portion of the piezoelectric thin film that exposes the first electrode;
• depositing a metal on the surface of the second crystalline quality portion of the piezoelectric thin film and depositing the metal in the via to contact the first electrode;
• and
• processing the metal to form a first electrode contact on the surface of the second crystalline quality portion of the piezoelectric thin film and to form a second electrode on the surface of the second crystalline quality portion of the piezoelectric thin film that is electrically isolated from the first electrode contact.