There is disclosed acoustic resonators and filter devices. An acoustic resonator device includes a piezoelectric plate, and an interdigital transducer (IDT) formed on a front surface of the piezoelectric plate. The IDT includes interleaved fingers. At least one of the interleaved fingers includes a first layer adjacent the piezoelectric plate and a second layer over the first layer, wherein a width of the first layer is constant, and wherein a width of the second layer varies along a length of the at least one interleaved finger.

Acoustic resonator devices and filters, and methods of making the same. An acoustic resonator includes a piezoelectric plate and an interdigital transducer (IDT) including interleaved fingers on the piezoelectric plate. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the piezoelectric plate. The acoustic resonator further includes a front-side dielectric layer on the piezoelectric plate between the fingers of the IDT, wherein a resonance frequency of the acoustic resonator device has an inverse dependence on a thickness of the front-side dielectric layer.

An acoustic filter includes a piezoelectric plate on a substrate. Portions of the piezoelectric plate form one or more diaphragms, each diaphragm spanning a respective cavity in the substrate. A conductor pattern on a front surface of the piezoelectric plate includes interdigital transducers (IDTs) of acoustic resonators including a shunt resonator and a series resonator. Interleaved fingers of each IDT are on a diaphragm of the one or more diaphragms. A first dielectric layer with a first thickness is between the fingers of the IDT of the shunt resonator, and a second dielectric layer with a second thickness less than the first thickness is between the fingers of the IDT of the series resonator. The piezoelectric plate and the IDTs are configured such that radio frequency signals applied to the IDTs excite respective primary shear acoustic modes within the diaphragms.

Acoustic filters and methods of fabrication are disclosed. A filter device includes a substrate and a single-crystal piezoelectric plate, a back surface of the piezoelectric plate attached to a surface of the substrate. The filter device includes a plurality of acoustic resonators including one or more shunt resonators and one or more series resonators. Each of the plurality of acoustic resonators includes an interdigital transducer (IDT) formed on the front surface of the piezoelectric plate, interleaved fingers of the IDT disposed on a respective diaphragm formed by a respective portion of the piezoelectric plate that spans a respective cavity in the substrate. A divided frequency setting layer is formed on at least some of the one or more shunt resonators but not on the one or more series resonators.

There is provided a piezoelectric vibrator element which is excellent in vibration characteristics, high in quality, and capable of suppressing a frequency fluctuation after a frequency adjustment. The piezoelectric vibrator element is provided with a piezoelectric plate having a pair of vibrating arm parts, an electrode film disposed on obverse and reverse surfaces of the piezoelectric plate, and weight metal films for a frequency adjustment disposed on the electrode film at the obverse surface side in the vibrating arm parts. The reverse surface of the vibrating arm part has a reverse side exposure part from which the piezoelectric plate is exposed. The obverse surface of the vibrating arm part has an obverse side exposure part from which the weight metal film and the electrode film are removed, and from which the piezoelectric plate is exposed. A whole of the obverse side exposure part overlaps the reverse side exposure part at a distance from the electrode film on the reverse surface viewed from a thickness direction of the piezoelectric plate.

Acoustic resonators and filters are disclosed. An acoustic resonator includes a substrate and a piezoelectric plate. A back surface of the piezoelectric plate is attached to the substrate except for a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A conductor pattern including an interdigital transducer (IDT) is formed on a front surface of the piezoelectric plate, interleaved fingers of the IDT disposed on the diaphragm. A front-side dielectric layer is formed on the front surface of the piezoelectric plate between, but not over, the IDT fingers. A back-side dielectric layer is formed on a back surface of the diaphragm. Thicknesses of the IDT fingers and the front-side dielectric layer are substantially equal. An acoustic impedance Zm of the IDT fingers and an acoustic impedance Zfd of the front-side dielectric layer satisfy the relationship 0.8Zm≤Zfd≤1.25Zm.

Methods of fabricating acoustic filters. A back-side frequency setting layer is formed on a surface of a substrate and/or a back surface of a piezoelectric plate. The piezoelectric plate is attached to the substrate with the back-side frequency setting layer sandwiched between the substrate and the piezoelectric plate. Portions of the piezoelectric plate and backside frequency setting layer form diaphragms spanning respective cavities in the substrate. A conductor pattern defining a plurality of acoustic resonators is formed on a front surface of the piezoelectric plate. Each of the acoustic resonators includes an interdigital transducer (IDT) with interleaved fingers disposed on a respective diaphragm. A front-side frequency setting layer is formed over the interleaved fingers and the front surface of the diaphragms of one or more shunt resonators. The back-side frequency setting layer is removed from the back surfaces of the diaphragms of one or more series resonators.

A filter device is provided that includes a substrate and a piezoelectric plate attached to the substrate. A conductor pattern is formed at a first surface of the piezoelectric plate and includes interdigital transducers of series and shunt resonators that each have interleaved fingers at respective diaphragms of the plate suspended. A first dielectric coating layer is formed over the interleaved fingers of the IDTs and on the first surface of the piezoelectric plate; and a second dielectric coating layer is formed on the second surface of the piezoelectric plate that is opposite the first surface. The second dielectric coating layer of the shunt resonator has a greater thickness than a thickness of the at least one second dielectric coating layer of the series resonator.

Acoustic filters and methods of fabricating acoustic filters are disclosed. A filter includes a single-crystal piezoelectric plate having a front surface and a back surface attached to a substrate, and a plurality of acoustic resonators including a first shunt resonator, a second shunt resonator, and one or more series resonators. Each of the plurality of acoustic resonators includes an interdigital transducer (IDT) formed on the front surface of the piezoelectric plate, interleaved fingers of the IDT disposed on a respective diaphragm formed by a portion of the piezoelectric plate that spans a cavity in the substrate. A frequency setting dielectric layer is formed over the first and second shunt resonators but not over the one or more series resonators. The frequency setting dielectric layer has a thickness t1 on the first shunt resonator and a thickness t2 on the second shunt resonator, where t1 is not equal to t2.

A method for manufacturing a film bulk acoustic resonance device is disclosed. The proposed method, wherein the device has a specific resonant frequency, includes: providing a substrate having a recess, wherein the recess has a height; configuring a first piezoelectric material layer on the substrate, and causing the recess to form an air gap; configuring a lower electrode on the first piezoelectric material layer; when the height is in a first range, causing a resonant frequency of the film bulk acoustic resonance device versus the height to have a first slope; when the height is in a second range, causing the resonant frequency versus the height to have a second slope; and causing the first slope to be smaller than the second slope.