A piezoelectric device that prevents defects due to pyroelectric charge without limiting how the piezoelectric device can be used includes a first metal layer located on a bonding surface of a piezoelectric single crystal substrate. A second metal layer is located on a bonding surface of a support substrate. The first and second metal layers are overlaid on each other to define a metal bonded layer. Subsequently, by oxidizing the metal bonded layer, a semi-conducting layer is formed.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate supported by the substrate. A portion of the piezoelectric plate suspended across a cavity in the substrate forms a diaphragm. A decoupling dielectric layer is on a front surface of the diaphragm. An interdigital transducer (IDT) has interleaved fingers on the decoupling dielectric layer over the diaphragm. The IDT and piezoelectric plate are configured such that a radio frequency signal applied to the IDT excites shear acoustic waves in the diaphragm.

An acoustic-wave device includes a first electrode located over a substrate. A piezoelectric film is located over the first electrode and at least partially overlaps the first electrode. A second electrode is located over the piezoelectric film and at least partially overlaps the first electrode and the piezoelectric film. A temperature sensor is located in a same layer level as the first or second electrode. A heater may also be located in a same layer level as the first electrode. A closed-loop system may operate using the temperature sensor and the heater to maintain an operating temperature that provides highly stable operation.

A composite structure for an acoustic wave device comprising a heterostructure includes: a useful layer of piezoelectric material, having a first face and a second face, the first face being arranged at a first bonding interface on a support substrate having a coefficient of thermal expansion less than that of the useful layer, wherein the composite structure further comprises a functional layer, an entire surface of which is arranged at a second bonding interface on the second face of the useful layer and having a coefficient of thermal expansion less than that of the useful layer. Methods are used for producing such a composite structure.