Methods of fabricating acoustic filters are disclosed. The back of a piezoelectric plate is bonded to a surface of a substrate. The thickness of the piezoelectric plate is measured at a plurality of positions. Excess material is removed from the front surface of the piezoelectric plate in accordance with the thickness measurements to improve the thickness uniformity of the piezoelectric plate. After removing the excess material, a conductor pattern including a plurality of ladder filter circuits is formed on the front surface. Each ladder filter circuit includes at least one shunt resonator and at least one series resonator, each of which has an interdigital transducer (IDT). Cavities are formed in the substrate such that portions of the piezoelectric plate form a plurality of diaphragms spanning respective cavities. After the cavities are formed, interleaved fingers of each IDT are on a respective one of the plurality of diaphragms.

Methods of fabricating acoustic filters are disclosed. The back of a piezoelectric plate is bonded to a surface of a substrate. The thickness of the piezoelectric plate is measured at a plurality of positions. Excess material is removed from the front surface of the piezoelectric plate in accordance with the thickness measurements to improve the thickness uniformity of the piezoelectric plate. After removing the excess material, a conductor pattern including a plurality of ladder filter circuits is formed on the front surface. Each ladder filter circuit includes at least one shunt resonator and at least one series resonator, each of which has an interdigital transducer (IDT). Cavities are formed in the substrate such that portions of the piezoelectric plate form a plurality of diaphragms spanning respective cavities. After the cavities are formed, interleaved fingers of each IDT are on a respective one of the plurality of diaphragms.

A method for manufacturing a piezoelectric vibration element that includes preparing a piezoelectric substrate; providing a first electrode layer on a first main surface of the piezoelectric substrate; arranging a mask on a side of the first main surface of the piezoelectric substrate, the mask including a center region and a peripheral region located along a periphery of the center region; and irradiating a radiation beam through the mask toward the first main surface of the piezoelectric substrate such that a larger amount of the radiation beam passes through the peripheral region than the center region of the mask so as to remove a part of the first electrode layer to form a first excitation electrode that decreases in thickness from the center region to the peripheral region of the mask on the first main surface of the piezoelectric substrate.

A method for manufacturing a piezoelectric vibration element that includes preparing a piezoelectric substrate; providing a first electrode layer on a first main surface of the piezoelectric substrate; arranging a mask on a side of the first main surface of the piezoelectric substrate, the mask including a center region and a peripheral region located along a periphery of the center region; and irradiating a radiation beam through the mask toward the first main surface of the piezoelectric substrate such that a larger amount of the radiation beam passes through the peripheral region than the center region of the mask so as to remove a part of the first electrode layer to form a first excitation electrode that decreases in thickness from the center region to the peripheral region of the mask on the first main surface of the piezoelectric substrate.

An elastic wave device includes a piezoelectric layer including a first main surface and a second main surface facing the first main surface, an acoustically reflective layer stacked on the first main surface of the piezoelectric layer, an excitation electrode disposed on the piezoelectric layer, and a support layer. The acoustically reflective layer overlaps at least the excitation electrode in a plan view of the piezoelectric layer from the side of the second main surface. The support layer surrounds the acoustically reflective layer in a plan view of the piezoelectric layer from the side of the second main surface.

An elastic wave device includes a piezoelectric layer including a first main surface and a second main surface facing the first main surface, an acoustically reflective layer stacked on the first main surface of the piezoelectric layer, an excitation electrode disposed on the piezoelectric layer, and a support layer. The acoustically reflective layer overlaps at least the excitation electrode in a plan view of the piezoelectric layer from the side of the second main surface. The support layer surrounds the acoustically reflective layer in a plan view of the piezoelectric layer from the side of the second main surface.

The present disclosure relates to a tunable Bulk Acoustic Wave (BAW) resonator with a top electrode, a bottom electrode, a piezoelectric layer sandwiched between the top electrode and the bottom electrode, and a reflection region underneath the bottom electrode. The reflection region includes a reflection layer and an ion-conductible structure between the bottom electrode and the reflection layer. Herein, the ion-conductible structure has a first terminal layer coupled to the bottom electrode, a second terminal layer coupled to the reflection layer, and an ion conductor between the first terminal layer and the second terminal layer. The ion conductor is eligible to transport ions between the first terminal layer and the second terminal layer, so as to achieve a mass-loading shift between the first terminal layer and the second terminal layer, and consequently, to tune a resonance frequency of the tunable BAW resonator.

Acoustic filters, resonators and methods are disclosed. An acoustic resonator device includes a substrate having a surface. A back surface of a single-crystal piezoelectric plate is 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. A conductor pattern is formed on the front surface of the piezoelectric plate, the conductor pattern including an interdigital transducer (IDTs), interleaved fingers of the IDT disposed on the diaphragm. A pitch of the interleaved fingers and a mark of the interleaved fingers are set in combination such that a resonance frequency of the acoustic resonator is equal to a predetermined target frequency.

Acoustic filters, resonators and methods are disclosed. An acoustic resonator device includes a substrate having a surface. A back surface of a single-crystal piezoelectric plate is 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. A conductor pattern is formed on the front surface of the piezoelectric plate, the conductor pattern including an interdigital transducer (IDTs), interleaved fingers of the IDT disposed on the diaphragm. A pitch of the interleaved fingers and a mark of the interleaved fingers are set in combination such that a resonance frequency of the acoustic resonator is equal to a predetermined target frequency.

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.