Multiple membrane thickness wafers using layer transfer acoustic resonators and method of manufacturing same

An acoustic resonator, comprising:

• a substrate;
• a first piezoelectric layer attached to the substrate via one or more intermediate layers, the piezoelectric layer comprising one or more first acoustic resonators;
• a second piezoelectric layer attached to the first piezoelectric layer opposite the substrate and comprising one or more second acoustic resonators;
• a first dielectric layer on the first piezoelectric layer;
• a second dielectric layer on the second piezoelectric layer;
• first and second interdigital transducers (IDTs) at the first and second piezoelectric layers, respectively;
• and
• an etch stop layer disposed between the first and second piezoelectric layers,
• wherein a portion of the first piezoelectric layer is removed between the substrate and the etch stop.

A radio frequency module, comprising:

• a filter device including a plurality of acoustic resonators;
• and
• a radio frequency circuit coupled to the filter device, the filter device and the radio frequency circuit being enclosed within a common package,
• wherein at least one of the plurality of acoustic resonators of the filter device includes:
• a substrate;
• a first piezoelectric layer having first and second surfaces that oppose each other, with the second surface facing the substrate and coupled thereto directly or via one or more intermediate layers;
• a second piezoelectric layer having first and second opposing surfaces, with the first surface coupled to the first surface of the first piezoelectric layer and opposite to the substrate;
• an etch stop layer disposed between the respective first surfaces of the first and second piezoelectric layers;
• and
• first and second interdigital transducers (IDTs) on at least one of the first and second piezoelectric layers, respectively,
• wherein a portion of the first piezoelectric layer is removed between the second surface of the first piezoelectric layer and the etch stop.