A piezoelectric thin film (PTF) is located above a carrier substrate. The PTF may be Z-cut LiNbO.sub.3 thin film adapted to propagate an acoustic wave in at least one of a first mode excited by an electric field oriented in a longitudinal direction along a length of the PTF or a second mode excited by the electric field oriented at least partially in a thickness direction of the PTF. A first interdigitated transducer (IDT) is disposed on a first end of the PTF. The first IDT is to convert a first electromagnetic signal, traveling in the longitudinal direction, into the acoustic wave. A second IDT is disposed on a second end of the PTF with a gap between the second IDT and the first IDT. The second IDT is to convert the acoustic wave into a second electromagnetic signal, and the gap determines a time delay of the acoustic wave.

A piezoelectric thin film (PTF) is located above a carrier substrate. The PTF can be an aluminum nitride thin film adapted to propagate an acoustic wave in at least one of a first mode excited by an electric field oriented at least partially in a longitudinal direction along a length of the PTF or a second mode excited by the electric field oriented in a thickness direction of the PTF. A first interdigitated transducer (IDT) is disposed on a first end of the PTF and converts a first electromagnetic signal, traveling in the longitudinal direction, into the acoustic wave. A second IDT is disposed on a second end of the PTF with a gap between the second IDT and the first IDT. The second IDT is to convert the acoustic wave into a second electromagnetic signal, and the gap determines a time delay of the acoustic wave.

A piezoelectric thin film (PTF) is located above a carrier substrate. The PTF may be X-cut LiNbO.sub.3 thin film adapted to propagate an acoustic wave in at least one of a first mode excited by an electric field oriented in a longitudinal direction along a length of the PTF or a second mode excited by the electric field oriented at least partially in a thickness direction of the PTF. A first interdigitated transducer (IDT) is disposed on a first end of the PTF. The first IDT is to convert a first electromagnetic signal, traveling in the longitudinal direction, into the acoustic wave. A second IDT is disposed on a second end of the PTF with a gap between the second IDT and the first IDT. The second IDT is to convert the acoustic wave into a second electromagnetic signal.

There is disclosed acoustic resonators and filter devices. An acoustic resonator includes a substrate having a surface and a single-crystal piezoelectric plate having 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 interleaved fingers include a first layer having a rectangular shape adjacent the diaphragm and a second layer over the first layer opposite the diaphragm, and wherein a width of the second layer varies along a length of each finger.

An acoustic resonator is fabricated by etching a recess in a silicon thermal oxide (TOX) upper layer of a silicon substrate and filling the recess with sacrificial polysilicon. A surface of the silicon TOX layer and the sacrificial polysilicon-filled recess are planarized. A back surface of a single-crystal piezoelectric plate is bonded to the planarized surface of the silicon TOX layer. Openings are formed through the piezoelectric plate and an interdigital transducer (IDT) is formed on a front surface of the piezoelectric plate such that interleaved fingers of the IDT are disposed over the sacrificial polysilicon-filled recess. The sacrificial polysilicon is removed from the recess to form a cavity such that a portion of the piezoelectric plate forms a diaphragm spanning the cavity and the interleaved fingers of the IDT are disposed on the diaphragm.

In a method of manufacturing a piezoelectric device in which a piezoelectric thin film on which functional conductors are formed is fixed to a support substrate by a fixing layer, an alignment mark is formed on one main surface of a light-transmitting piezoelectric substrate. A sacrificial layer is formed on a main surface of the piezoelectric substrate with reference to the alignment mark and the fixing layer is formed so as to cover the sacrificial layer and is bonded to the support substrate. The piezoelectric thin film is formed by being separated from the piezoelectric substrate and the functional conductors are formed on the surface of the piezoelectric thin film with reference to the alignment mark. The piezoelectric device is able to be manufactured while positions of formation regions of conductors are adjusted efficiently.

A bulk acoustic wave resonator device comprises bottom and top electrodes (120, 360). A piezoelectric layer (355) sandwiched therebetween has a thickness in the active resonator area different from the thickness in the surrounding area. A method of manufacturing the device comprises a bonding of a piezoelectric wafer to a carrier wafer and splitting a portion of the piezoelectric wafer by an ion-cut technique. Different thicknesses of the piezoelectric layer in the active area and the surrounding area are achieved by implanting ions at different depths.

Disclosed is a method of manufacturing a piezoelectric thin film resonator on a non-silicon substrate, including the following steps: depositing a copper thin film on a silicon wafer; coating photoresist on the copper thin film to perform photoetching so as to remove photoresist in an air gap region under the piezoelectric thin film resonator to be disposed; electroplating-depositing a copper layer, and removing photoresist to obtain a stepped peel sacrifice layer; coating polyimide and performing imidization by heat treatment, making a sandwich structure of the piezoelectric thin film resonator above the polyimide layer; performing etching for the polyimide layer in a region not covered by the piezoelectric thin film resonator by oxygen plasma; placing the obtained device into a copper corrosion solution to dissolve the copper around and under the piezoelectric thin film resonator, attaching a drum coated with polyvinyl alcohol glue onto the piezoelectric thin film resonator, releasing and peeling it from the silicon wafer and then transferring it to a desired non-silicon substrate; washing the drum with hot water to separate the drum from the piezoelectric thin film resonator so as to complete the manufacturing process.

An acoustic resonator includes a membrane layer disposed on an insulating layer; a cavity formed by the insulating layer and the membrane layer; a resonating portion disposed on the cavity and having a first electrode, a piezoelectric layer, and a second electrode stacked thereon; a protective layer disposed on the resonating portion; and a hydrophobic layer formed on the protective layer.

Filter devices and methods of fabrication are disclosed. A filter device includes a piezoelectric plate attached to a substrate, portions of the piezoelectric plate forming diaphragms spanning respective cavities in the substrate. A conductor pattern formed on a surface of the piezoelectric plate includes a plurality of interdigital transducers (IDTs) of a respective plurality of acoustic resonators including a shunt resonator and a series resonator, interleaved fingers of each of the plurality of IDTs disposed on one of the diaphragms. Radio frequency signals applied to the IDTs excite respective primary shear acoustic modes in the respective diaphragms. A thickness of a first dielectric layer disposed on the front surface between the fingers of the IDT of the shunt resonator is greater than a thickness of a second dielectric layer disposed on the front surface between the fingers of the IDT of the series resonator.