Acoustic resonator devices and methods are disclosed. An acoustic resonator device includes a piezoelectric plate having opposed front and back surfaces. A first electrode and a second electrode are formed on the front surface of the piezoelectric plate, the first and second electrodes and the piezoelectric plate configured such that a radio frequency signal applied between the first and second electrodes excites a shear primary acoustic mode in the piezoelectric plate. The first electrode and the second electrode have trapezoidal cross-sectional shapes. A sidewall angle of at least one side surface of the first electrode and a sidewall angle of at least one side surface of the second electrode are greater than or equal to 70 degrees and less than or equal to 110 degrees.

Aspects of this disclosure relate to bulk acoustic wave resonators. A bulk acoustic wave resonator includes a patterned mass loading layer that affects a resonant frequency of the bulk acoustic wave resonator. The patterned mass loading layer can have a duty factor in a range from 0.2 to 0.8 in a main acoustically active region of the bulk acoustic wave resonator. Related filters, acoustic wave dies, radio frequency modules, wireless communications devices, and methods are disclosed.

A BAW resonator filter can include a BAW resonator pass-band filter ladder, the BAW resonator pass-band filter ladder can be configured to pass frequency components of an input signal in a pass-band of frequencies received at an input node of the BAW resonator pass-band filter ladder to an output node of the BAW resonator pass-band filter ladder. A first rejection-band series resonator can be coupled in series between an input port of the BAW resonator pass-band filter ladder and the input node, the first rejection-band series resonator can have a first anti-resonant frequency peak in a rejection-band of frequencies that is less than the pass-band of frequencies. A second rejection-band series resonator can be coupled in series between an output port of the BAW resonator filter and the output node, the second rejection-band series resonator can have a second anti-resonant frequency peak in the rejection-band of frequencies.

A filter circuit includes a plurality of first resonators provided in a series arm, a plurality of second resonators provided in a parallel arm, and at least one or more third resonators that are electrically connected in series with each other and are electrically connected in parallel with the first resonators in the series arm. An anti-resonant frequency of the third resonators is lower than an anti-resonant frequency of the second resonators. A combined capacitance of the at least one or more third resonators electrically connected in series with each other is smaller than an electrostatic capacitance of the second resonators.

A method of manufacture for an acoustic resonator or filter device. In an example, the present method can include forming metal electrodes with different geometric areas and profile shapes coupled to a piezoelectric layer overlying a substrate. These metal electrodes can also be formed within cavities of the piezoelectric layer or the substrate with varying geometric areas. Combined with specific dimensional ratios and ion implantations, such techniques can increase device performance metrics. In an example, the present method can include forming various types of perimeter structures surrounding the metal electrodes, which can be on top or bottom of the piezoelectric layer. These perimeter structures can use various combinations of modifications to shape, material, and continuity. These perimeter structures can also be combined with sandbar structures, piezoelectric layer cavities, the geometric variations previously discussed to improve device performance metrics.

Acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having front and back surfaces. The back surface is attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern formed is formed on the front surface of the piezoelectric plate, including an interdigital transducer (IDT) with interleaved fingers of the IDT on the diaphragm. The substrate and the piezoelectric plate are the same material.

A radio frequency filter includes at least a first sub-filter and a second sub-filter connected in parallel between a first port and a second port. Each of the sub-filters has a piezoelectric plate having front and back surfaces, the back surface attached to a substrate, and portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern is formed on the front surface of the plate, the conductor pattern includes interdigital transducers (IDTs) of a respective plurality of resonators, with interleaved fingers of each IDT disposed on a respective diaphragm of the plurality of diaphragms. A thickness of the portions of the piezoelectric plate of the first sub-filter is different from a thickness of the portions of the piezoelectric plate of the second sub-filter.

Disclosed herein are embodiments of a ladder-type filter comprising a plurality of series arm resonators and a plurality of parallel arm resonators, at least one of the plurality of series arm resonators including a piezoelectric substrate and an interdigital transducer electrode disposed on the piezoelectric substrate, an aperture W1 of the interdigital transducer electrode being configured to be less than 13λ, where λ is a wavelength of a surface acoustic wave excited by the interdigital transducer electrode. The relationship between the aperture W1 and the wavelength λ can be W1 < 13λ, W1 < 11λ, W1 < 4λ, or W1 > 6λ.

Filter devices and fabrication methods are disclosed. A filter device includes a piezoelectric plate and a conductor pattern on a front surface of the piezoelectric plate. The conductor pattern includes interdigital transducers (IDTs) of a plurality of transversely-excited film bulk acoustic resonators (XBARs) and a plurality of conductors connecting the plurality of XBARs in a ladder filter circuit architecture. The plurality of conductors includes a first conductor adjacent to a second conductor. An opening is provided through the piezoelectric plate between the first conductor and the second conductor.

Disclosed are a resonator and a manufacturing method thereof, a filter, and an electronic device. The resonator includes a substrate, a Bragg reflection layer, and a piezoelectric layer that are sequentially stacked. A first electrode is disposed on a surface that is of the piezoelectric layer and that faces the Bragg reflection layer, a second electrode is disposed on a surface that is of the piezoelectric layer and that is away from the Bragg reflection layer, a border ring is disposed on a surface that is of the second electrode and that is away from the piezoelectric layer, and the resonator has a first resonance region and a second resonance region corresponding to the border ring.