A structure includes a substrate including a wafer or a portion thereof; and a piezoelectric bulk material layer comprising a first portion deposited onto the substrate and a second portion deposited onto the first portion, the second portion comprising an outer surface having a surface roughness (Ra) of 4.5 nm or less. Methods for depositing a piezoelectric bulk material layer include depositing a first portion of bulk layer material at a first incidence angle to achieve a predetermined c-axis tilt, and depositing a second portion of the bulk material layer onto the first portion at a second incidence angle that is smaller than the first incidence angle. The second portion has a second c-axis tilt that substantially aligns with the first c-axis tilt.

A structure includes a substrate including a wafer or a portion thereof; and a piezoelectric bulk material layer comprising a first portion deposited onto the substrate and a second portion deposited onto the first portion, the second portion comprising an outer surface having a surface roughness (Ra) of 4.5 nm or less. Methods for depositing a piezoelectric bulk material layer include depositing a first portion of bulk layer material at a first incidence angle to achieve a predetermined c-axis tilt, and depositing a second portion of the bulk material layer onto the first portion at a second incidence angle that is smaller than the first incidence angle. The second portion has a second c-axis tilt that substantially aligns with the first c-axis tilt.

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.

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.

Bulk acoustic wave resonators of two or more different filters can be on a common die. The two filters can be included in a multiplexer, such as a duplexer, or implemented as standalone filters. With bulk acoustic wave resonators of two or more filters on the same die, the filters can be implemented in less physical space compared to implementing the same filters of different die. Related methods, radio frequency systems, radio frequency modules, and wireless communication devices are also disclosed.

Filter devices and methods are disclosed. A single-crystal piezoelectric plate is attached to substrate, portions of the piezoelectric plate forming a plurality of diaphragms spanning respective cavities in the substrate. A conductor pattern formed on the piezoelectric plate defines a low band filter including low band shunt resonators and low band series resonators and a high band filter including high band shunt resonators and high band series resonators. Interleaved fingers of interdigital transducers (IDTs) of the low band shunt resonators are disposed on respective diaphragms having a first thickness, interleaved fingers of IDTs of the high band series resonators are disposed on respective diaphragms having a second thickness less than the first thickness, and interleaved fingers of IDTs of the low band series resonators and the high band shunt resonators are disposed on respective diaphragms having thicknesses intermediate the first thickness and the second thickness.

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 0.8ZmZfd1.25Zm.

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 0.8ZmZfd1.25Zm.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate and a single-crystal piezoelectric plate. A back surface of a supported portion of the piezoelectric plate is attached to a surface of the substrate. A portion of the piezoelectric plate forms a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on a front surface of the piezoelectric plate. The IDT includes first and second busbars, and interleaved fingers extending alternately from the first and second busbars. Overlapping portions of the interleaved fingers are disposed on the diaphragm. At least portions of both the first and second busbars are disposed on the supported portion of the piezoelectric plate. The piezoelectric plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a primary shear acoustic mode within the diaphragm.

Techniques for improving Bulk Acoustic Wave (BAW) resonator structures are disclosed, including fluidic systems, oscillators and systems that may include such devices. A bulk acoustic wave (BAW) resonator may comprise a substrate and a first layer of piezoelectric material. The bulk acoustic wave (BAW) resonator may comprise a top electrode. A sensing region may be acoustically coupled with the top electrode of the bulk acoustic wave (BAW) resonator.