An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having a back surface bonded to the substrate. An interdigital transducer (IDT) is formed on the front surface of the piezoelectric plate and has interleaved fingers on a diaphragm spanning a cavity in the substrate. An etch-stop layer is formed on the front surface of the piezoelectric plate between the interleaved fingers. A portion of the piezoelectric plate and the etch-stop layer form the diaphragm. The etch-stop layer is impervious to the etch process used to form the interleaved fingers. The etch-stop layer may be formed on the piezoelectric plate between but not under the interleaved fingers. In other cases, the etch-stop layer is formed on the piezoelectric plate between and under the interleaved fingers.

An acoustic resonator is fabricated by forming a patterned first photoresist mask on a piezoelectric plate at locations of a desired interdigital transducer (IDT) pattern. An etch-stop layer is then deposited on the plate and first photoresist mask. The first photoresist mask is removed to remove parts of the etch-stop and expose the plate. An IDT conductor material is deposited on the etch stop and the exposed plate. A patterned second photoresist mask is then formed on the conductor material at locations of the IDT pattern. The conductor material is then etched over and to the etch-stop to form the IDT pattern which has interleaved fingers on a diaphragm to span a substrate cavity. A portion of the plate and the etch-stop form the diaphragm. The etch-stop and photoresist mask are impervious to this etch. The second photoresist mask is removed to leave the IDT pattern.

Acoustic resonator devices, filters, and methods are disclosed. An acoustic resonator includes a substrate and a lithium niobate (LN) plate having front and back surfaces and a thickness ts. The back surface is attached to a surface of the substrate. A portion of the LN plate forms a diaphragm spanning a cavity in the substrate. An interdigital transducer (IDT) is formed on the front surface of the LN plate with interleaved fingers of the IDT disposed on the diaphragm. The LN plate and the IDT are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic wave in the diaphragm. Euler angles of the LN plate are [0, , 0 ], where 060. A thickness of the interleaved fingers of the IDT is greater than or equal to 0.8 ts and less than or equal to 2.0 ts.

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

An acoustic resonator includes: a central portion; an extension portion extended outwardly of the central portion; a first electrode, a piezoelectric layer, and a second electrode sequentially stacked on a substrate, in the central portion; and an insertion layer disposed below the piezoelectric layer in the extension portion, wherein the piezoelectric layer includes a piezoelectric portion disposed in the central portion, and a bent portion disposed in the extension portion and extended from the piezoelectric portion at an incline depending on a shape of the insertion layer.

A single-crystal bulk acoustic wave resonators with better performance and better manufacturability and a process for fabricating the same are described. A low-acoustic-loss layer of one or more single-crystal and/or poly-crystal piezoelectric materials is epitaxially grown and/or physically deposited on a surrogate substrate, followed with the formation of a bottom electrode and then a support structure on a first side of the piezoelectric layer. The surrogate substrate is subsequently removed to expose a second side of the piezoelectric layer that is opposite to the first side. A top electrode is then formed on the second side of the piezoelectric layer, followed by further processes to complete the BAW resonator and filter fabrication using standard wafer processing steps. In some embodiments, the support structure has a cavity or an acoustic mirror adjacent the first electrode layer to minimize leakage of acoustic wave energy.

Acoustic resonator devices and filters are disclosed. A piezoelectric plate is attached to a substrate, a portion of the piezoelectric plate forming a diaphragm spanning a cavity in the substrate. A first conductor pattern is formed on a surface of the piezoelectric plate. The first conductor pattern includes interleaved fingers of an interdigital transducer disposed on the diaphragm, and a first plurality of contact pads. A second conductor pattern is formed on a surface of a base, the second conductor pattern including a second plurality of contact pads. Each pad of the first plurality of contact pads is directly bonded to a respective pad of the second plurality of contact pads. A ring-shaped seal is form between a perimeter of the piezoelectric plate and a perimeter of the base.

A communication system using a single crystal acoustic resonator device. The device includes a piezoelectric substrate with a piezoelectric layer formed overlying a transfer substrate. A topside metal electrode is formed overlying the substrate. A topside micro-trench is formed within the piezoelectric layer. A topside metal with a topside metal plug is formed within the topside micro-trench. First and second backside cavities are formed within the transfer substrate under the topside metal electrode. A backside metal electrode is formed under the transfer substrate, within the first backside cavity, and under the topside metal electrode. A backside metal plug is formed under the transfer substrate, within the second backside cavity, and under the topside micro-trench. The backside metal plug is connected to the topside metal plug and the backside metal electrode. The topside micro-trench, the topside metal plug, the second backside cavity, and the backside metal plug form a micro-via.

An acoustic wave resonator includes a resonating part disposed on and spaced apart from a substrate by a cavity, the resonating part including a membrane layer, a first electrode, a piezoelectric layer, and a second electrode that are sequentially stacked. 0 Mg170 may be satisfied, Mg being a difference between a maximum thickness and a minimum thickness of the membrane layer disposed in the cavity.

An acoustic wave resonator includes a resonating part disposed on and spaced apart from a substrate by a cavity, the resonating part including a membrane layer, a first electrode, a piezoelectric layer, and a second electrode that are sequentially stacked. 0 Mg170 may be satisfied, Mg being a difference between a maximum thickness and a minimum thickness of the membrane layer disposed in the cavity.