A longitudinally coupled resonator acoustic wave filter including IDT electrodes including a first IDT electrode and a second IDT electrode, and first and second reflectors, in which the IDT electrodes have respective hot-side comb-shaped electrodes and respective ground-side comb-shaped electrodes, the hot-side comb-shaped electrodes of the first IDT electrodes are electrically connected to at least one of the first and second reflectors, the second IDT electrodes are between the IDT electrode and the first reflector and between the IDT electrode and the second reflector respectively, the hot-side comb-shaped electrodes of the IDT electrodes are connected to one of an input end and an output end, and the hot-side comb-shaped electrodes of the IDT electrodes are connected to the other of the input end and the output end.

Certain aspects of the present disclosure provide a surface acoustic wave (SAW) device with one or more intermediate layers for reduced self-heating and methods for fabricating such a SAW device. One example SAW device generally includes a piezoelectric layer and an interdigital transducer (IDT) disposed above the piezoelectric layer. The IDT generally includes a first electrode having a first busbar and a first plurality of fingers. The first electrode generally includes a first copper layer disposed above the piezoelectric layer, a first intermediate layer disposed above the first copper layer, the first intermediate layer comprising a different material than the first copper layer, and a second copper layer disposed above the first intermediate layer.

Certain aspects of the present disclosure provide a surface acoustic wave (SAW) device with one or more intermediate layers for reduced self-heating and methods for fabricating such a SAW device. One example SAW device generally includes a piezoelectric layer and an interdigital transducer (IDT) disposed above the piezoelectric layer. The IDT generally includes a first electrode having a first busbar and a first plurality of fingers. The first electrode generally includes a first copper layer disposed above the piezoelectric layer, a first intermediate layer disposed above the first copper layer, the first intermediate layer comprising a different material than the first copper layer, and a second copper layer disposed above the first intermediate layer.

An acoustic wave device has a multilayer piezoelectric substrate (MPS) structure and a multilayer interdigital transducer electrode (IDT). The multilayer piezoelectric substrate includes a piezoelectric layer over a support substrate. An additional (functional) layer can optionally be interposed between the piezoelectric layer and the support substrate, which can facilitate bonding between these layers and provide temperature compensation. The multilayer IDT is disposed over the piezoelectric layer and includes a first layer of a first material with higher density and a second layer of a different material with lower density. The interdigital transducer electrode also includes (mass loading) strips disposed over (e.g., adjacent, in contact with) the second layer, which advantageously facilitate suppression of transverse mode.

Aspects of this disclosure relate to a radio frequency system with an antenna, a radio frequency amplifier, and parallel acoustic wave filters. The parallel acoustic wave filters can each be a band pass filter having a passband and resonator area. The passbands of the parallel acoustic filters can be overlap in an overlap band. One of the parallel acoustic wave filters can have a smaller resonator area than another of the parallel acoustic wave filters.

A method of making an electronics package with a multi-layer piezoelectric substrate includes bonding a piezoelectric layer over a substrate. The method also includes applying a polyimide layer over an outer boundary of the piezoelectric layer so that the polyimide layer is interposed between the piezoelectric layer and a metal portion (e.g., of copper (Cu)) to inhibit (e.g., prevent) stresses from the metal layer damaging the piezoelectric layer.

A method of making an electronics package with a multi-layer piezoelectric substrate includes bonding a piezoelectric layer over a substrate. The method also includes applying a polyimide layer over an outer boundary of the piezoelectric layer so that the polyimide layer is interposed between the piezoelectric layer and a metal portion (e.g., of copper (Cu)) to inhibit (e.g., prevent) stresses from the metal layer damaging the piezoelectric layer.

A multiplexer includes a transmission-side filter electrically connected to a common terminal and a transmission input terminal, and a transmission-side filter electrically connected to the common terminal and a transmission input terminal. The transmission-side filter includes a plurality of series arm resonators and a plurality of parallel arm resonators. Capacitance elements are respectively electrically connected in parallel to the series arm resonator and the parallel arm resonator, which are connected most proximately to the common terminal. IDT electrodes of a series arm resonator and a parallel arm resonator connected most proximately to the common terminal do not include a thinning electrode, and others of the series arm resonators and the parallel arm resonators include thinning electrodes.

A multimode longitudinally coupled surface acoustic wave resonator is disclosed. The multimode longitudinally coupled surface acoustic wave resonator can include a first interdigital transducer electrode that is positioned over a piezoelectric layer. The first interdigital transducer electrode includes fingers having a first pitch. The multimode longitudinally coupled surface acoustic wave resonator can also include first and second sets of reflectors that are positioned over the piezoelectric layer. The first and second sets of reflectors include a first number of reflectors having a second pitch and a second number of reflectors having a third pitch, respectively. The first pitch is greater than the second pitch. The multimode longitudinally coupled surface acoustic wave resonator can further include a second interdigital transducer electrode that is positioned over the piezoelectric layer and between the first interdigital transducer electrode and the first set of reflectors. The second interdigital transducer electrode includes fingers having a fourth pitch.

A surface acoustic wave (SAW) filter includes a bottom substrate, a piezoelectric layer disposed above the bottom substrate, the piezoelectric layer having a bottom surface facing the bottom substrate and a top surface opposite to the bottom surface, a cavity disposed below the piezoelectric layer, an interdigital transducer (IDT) disposed on the top surface of the piezoelectric layer, and a back electrode disposed on the bottom surface of the piezoelectric layer. At least a portion of the back electrode is exposed in the cavity.