A frequency adjustment method is provided for a piezoelectric resonator including a first vibrator, a second vibrator, a third vibrator, and a supporting portion. The second and the third vibrators connect to ends positioned along a vibration direction of a width-longitudinal mode in the first vibrator. The supporting portion is connected to two ends positioned along a vibration direction of the length-longitudinal mode in the first vibrator. The method includes: setting the second vibrator to a first region, a second region, and a third region along the vibration direction of the width-longitudinal mode; setting the third vibrator to a first region, a second region, and a third region along the vibration direction of the width-longitudinal mode; and performing the frequency adjustment by reducing or adding mass of at least one of the first region and the third region in each of the second vibrator and the third vibrator.

A filter includes: piezoelectric thin film resonators, each including a substrate, a piezoelectric film located on the substrate, a lower electrode and an upper electrode facing each other across at least a part of the piezoelectric film, and an insertion film inserted in the piezoelectric film, located in at least a part of an outer peripheral region within a resonance region, and not located in a center region of the resonance region, the resonance region being a region where the lower electrode and the upper electrode face each other across the piezoelectric film, wherein at least two piezoelectric thin film resonators out of the piezoelectric thin film resonators have different widths of the insertion films within the resonance regions.

In a crystal resonator, a frequency adjustment metal film made of a base metal layer and a metal layer is formed on a first main surface of a second sealing member. The frequency adjustment of the crystal resonator is performed by: irradiating the frequency adjustment metal film with a laser from an outside of the second sealing member to heat the base metal layer; and melting and evaporating at least part of the metal layer so that the evaporated metal layer is adhered to a second excitation electrode. The irradiation with the beam is started from an outside of a region of the metal layer. In a beam scanning direction, an end part of the metal layer is located in an inside of an end part of the base metal layer.

BAW devices include a piezoelectric layer with a first electrode layer on one face and a second electrode layer on the opposite face. The piezoelectric layer and electrode layers determine a coupling efficiency of the BAW devices, which is a measure of the acoustic response of the piezoelectric layer to an input signal. In a BAW device, a first side of the first electrode layer comprises a first material adjacent to a first face of the piezoelectric layer, and a second side of the first electrode layer, opposite to the first face of the piezoelectric layer, comprises a second material, where the first material and the second material have different acoustic impedances. An electrode layer with an acoustic impedance gradient increases the coupling efficiency of the BAW devices.

Techniques for improving acoustic wave device structures are disclosed, including filters and systems that may include such devices. An acoustic wave device may include a substrate. The acoustic wave device may include first and second layers of piezoelectric material acoustically coupled with one another, in which the first layer of piezoelectric material has a first piezoelectric axis orientation, and the second layer of piezoelectric material has a second piezoelectric axis orientation that substantially opposes the first piezoelectric axis orientation of the first layer of piezoelectric material. The acoustic wave device may include an interposer layer interposed between the first and second layers of piezoelectric material. The interposer may facilitate an enhancement of an electromechanical coupling coefficient of the acoustic wave device.

Techniques for improving acoustic wave device structures are disclosed, including at least filters and systems that may include such devices. An acoustic wave device may include at least a substrate. The acoustic wave device may include at least a first piezoelectric layer and a second piezoelectric layer and a third piezoelectric layer. The second piezoelectric layer may have a second piezoelectric axis orientation. The third piezoelectric layer may have a third piezoelectric axis orientation that substantially opposes the second piezoelectric axis orientation of the second piezoelectric layer. The acoustic wave device may include an interposer layer coupled between the second piezoelectric layer and the third piezoelectric layer.

A method for manufacturing an acoustic wave device with an excellent frequency-temperature profile is performed such that the acoustic wave device produced includes a piezoelectric substrate, an IDT electrode located on the piezoelectric substrate, and a dielectric film mainly including Si and O and arranged on the piezoelectric substrate to cover the IDT electrode. The dielectric film is formed by sputtering in a sputtering gas containing H.sub.2O.

An acoustic wave device includes: a substrate; a piezoelectric film located on the substrate; a lower electrode and an upper electrode facing each other across the piezoelectric film, at least one of the lower electrode and the upper electrode including a first conductive film and a second conductive film formed on the first conductive film; an insulating film sandwiched between the first conductive film and the second conductive film and having a temperature coefficient of an elastic constant opposite in sign to a temperature coefficient of an elastic constant of the piezoelectric film; and a third conductive film formed on edge surfaces of the insulating film and the second conductive film and causing electrical short circuits between the first conductive film and the second conductive film.

A method of manufacture for an acoustic resonator or filter device. In an example, the present method can include forming metal electrodes with different geometric areas and profile shapes coupled to a piezoelectric layer overlying a substrate. These metal electrodes can also be formed within cavities of the piezoelectric layer or the substrate with varying geometric areas. Combined with specific dimensional ratios and ion implantations, such techniques can increase device performance metrics. In an example, the present method can include forming various types of perimeter structures surrounding the metal electrodes, which can be on top or bottom of the piezoelectric layer. These perimeter structures can use various combinations of modifications to shape, material, and continuity. These perimeter structures can also be combined with sandbar structures, piezoelectric layer cavities, the geometric variations previously discussed to improve device performance metrics.

A bulk acoustic wave device and a method of forming the same is disclosed. The bulk acoustic wave device can include a piezoelectric layer positioned between a first electrode and a second electrode. The bulk acoustic wave device can include a frequency adjustment layer over the second electrode. The bulk acoustic wave device can include a bonding layer between the second electrode and the frequency adjustment layer. A bonding strength between the second electrode and the frequency adjustment layer with the bonding layer is greater than a bonding strength between the second electrode and the frequency adjustment layer without the bonding layer. The bonding layer can have a thickness in a range between 1 nanometer and 20 nanometers.