Methods of fabricating acoustic resonators are disclosed. A back surface of a single-crystal piezoelectric plate is bonded to a surface of a substrate. A conductor pattern is formed on the front surface of the piezoelectric plate, the conductor pattern including a plurality of interdigital transducers (IDTs) of a plurality of resonators. A dielectric passivation/tuning layer is formed over the conductor pattern and the front surface of the piezoelectric plate. Electrical measurements are made on at least some of the plurality of resonators. Material is selectively removed from the dielectric passivation/tuning layer in accordance with the electrical measurements. After removing material from the dielectric passivation/tuning layer, cavities are formed in the substrate such that interleaved fingers of each IDT are disposed on a respective diaphragm spanning a respective cavity

Methods of fabricating acoustic resonators are disclosed. A back surface of a piezoelectric plate is bonded to a surface of a substrate. Thickness measurements are made at a plurality of positions on the piezoelectric plate. Excess material is removed from the front surface of the piezoelectric plate in accordance with the thickness measurements to improve a thickness uniformity of the piezoelectric plate. A conductor pattern is formed on the front surface, the conductor pattern including a plurality of interdigital transducers (IDTs) of a plurality of resonators. Cavities are formed in the substrate such that portions of the single-crystal piezoelectric plate form a plurality of diaphragms spanning respective cavities, wherein interleaved fingers of each IDT of the plurality of IDTs are disposed on a respective one of the plurality of diaphragms.

A bulk-acoustic wave resonator includes: a membrane layer disposed on a substrate and forming a cavity; a lower electrode disposed on the membrane layer; a piezoelectric layer disposed on the lower electrode; an upper electrode disposed on the piezoelectric layer, and including a frame part disposed at an edge of an active area and having a thickness greater than that of a portion of the upper electrode disposed in a central portion of the active area; and a frequency adjusting layer disposed on the piezoelectric layer and the upper electrode. The frequency adjusting layer is excluded from an inclined surface of the frame part, or a thickness of a portion of the frequency adjusting layer on the inclined surface is less than that of other portions of the frequency adjusting layer. The frequency adjusting layer is disposed on a portion of the piezoelectric layer protruding from the upper electrode.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A direction of acoustic energy flow of the primary acoustic mode is substantially orthogonal to the front and back surfaces of the diaphragm. The diaphragm is contiguous with the piezoelectric plate around at least 50% of a periphery of the diaphragm.

A method of reducing non-uniformity in the resonance frequencies of a surface acoustic wave (SAW) device, the SAW device comprising a silicon oxide layer comprising an oxide of silicon deposited over interdigital transducers on a piezoelectric substrate by reactive sputtering. The method comprises positioning a piezoelectric substrate having interdigital transducers on a substrate support, then depositing a silicon oxide layer comprising an oxide of silicon over the piezoelectric substrate and the interdigital transducers to form a SAW device. The substrate support is positioned relative to a sputtering target so that the silicon oxide layer of the SAW device has an arithmetic mean surface roughness (R.sub.a) of 11 angstroms or less.

Acoustic resonator devices and filters are disclosed. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having parallel front and back surfaces, the back surface attached to the surface of the substrate except for a portion of the piezoelectric plate forming a diaphragm that spans a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the single-crystal piezoelectric plate such that interleaved fingers of the IDT are disposed on the diaphragm. The IDT is configured to excite a primary acoustic mode in the diaphragm in response to a radio frequency signal applied to the IDT. A direction of acoustic energy flow of the primary acoustic mode is substantially orthogonal to the front and back surfaces of the diaphragm. The diaphragm is contiguous with the piezoelectric plate around at least 50% of a perimeter of the cavity.

In an array of single crystal acoustic resonators, the effective coupling coefficient of first and second strained single crystal filters are individually tailored in order to achieve desired frequency responses. In a duplexer embodiment, the effective coupling coefficient of a transmit band-pass filter is lower than the effective coupling coefficient of a receive band-pass filter of the same duplexer. The coefficients can be tailored by varying the ratio of the thickness of a piezoelectric layer to the total thickness of electrode layers or by forming a capacitor in parallel with an acoustic resonator within the filter for which the effective coupling coefficient is to be degraded. Further, a strained piezoelectric layer can be formed overlying a nucleation layer characterized by nucleation growth parameters, which can be configured to modulate a strain condition in the strained piezoelectric layer to adjust piezoelectric properties for improved performance in specific applications.

A bulk acoustic wave resonator includes a substrate protective layer disposed on a top surface of a substrate, a cavity defined by a membrane layer and the substrate, and a resonating part disposed on the membrane layer. The membrane layer includes a first layer and a second layer, the second layer having the same material as the first layer and having a density greater than that of the first layer.

An acoustic resonator includes: a resonating unit including a resonating unit including a piezoelectric layer and first and second electrodes disposed on a lower side and an upper side of the piezoelectric layer, respectively; a substrate disposed on a lower side of the resonating unit; a support unit providing a cavity between the substrate and the resonating unit; and an intermediate metal layer separated from the second electrode and disposed in the resonating unit such that at least a portion thereof is surrounded by the piezoelectric layer and the second electrode.

A method for fabricating bulk acoustic wave resonator with mass adjustment structure, comprising following steps of: forming a sacrificial structure mesa on a substrate; etching the sacrificial structure mesa such that any two adjacent parts have different heights, a top surface of a highest part of the sacrificial structure mesa is coincident with a mesa top extending plane; forming an insulating layer on the sacrificial structure mesa and the substrate; polishing the insulating layer to form a polished surface; forming a bulk acoustic wave resonance structure including a top electrode, a piezoelectric layer and a bottom electrode on the polished surface; etching the sacrificial structure mesa to form a cavity; the insulating layer between the polished surface and the mesa top extending plane forms a frequency tuning structure, the insulating layer between the mesa top extending plane and the cavity forms a mass adjustment structure.