Transversely-excited film bulk acoustic resonators with piezoelectric diaphragm supported by piezoelectric substrate

An acoustic resonator device comprising:

• a substrate;
• a single-crystal piezoelectric plate coupled to the surface of the substrate and having a portion that spans a cavity;
• a buried oxide layer between the substrate and the piezoelectric plate, wherein the substrate is attached to the piezoelectric plate via the buried oxide layer, and wherein the buried oxide layer does not extend across the cavity;
• a conductor pattern at a surface of the piezoelectric plate, the conductor pattern comprising an interdigital transducer (IDT) having interleaved fingers at the portion of the piezoelectric plate that spans the cavity, wherein the substrate and the piezoelectric plate include a same material;
• and
• an etch stop at an edge of the cavity.

An acoustic resonator device comprising:

• a substrate;
• a single-crystal piezoelectric plate coupled to the substrate and having a portion that spans a cavity;
• a buried oxide layer between the substrate and the piezoelectric plate, wherein the substrate is attached to the piezoelectric plate via the buried oxide layer;
• a conductor pattern at a surface of the piezoelectric plate, the conductor pattern comprising an interdigital transducer (IDT) having interleaved fingers at the portion of the piezoelectric plate that spans the cavity, wherein the substrate and the piezoelectric plate are a same material;
• and
• at least one through hole extending through the portion of the piezoelectric plate that spans the cavity to the cavity.