Disclosed herein are embodiments of a ladder-type filter comprising a plurality of series arm resonators and a plurality of parallel arm resonators, at least one of the plurality of series arm resonators including a piezoelectric substrate and an interdigital transducer electrode disposed on the piezoelectric substrate, an aperture W1 of the interdigital transducer electrode being configured to be less than 13λ, where λ is a wavelength of a surface acoustic wave excited by the interdigital transducer electrode. The relationship between the aperture W1 and the wavelength λ can be W1 < 13λ, W1 < 11λ, W1 < 4λ, or W1 > 6λ.

Embodiments of the invention relate to a surface acoustic wave device including a piezoelectric substrate, an interdigital transducer electrode on the piezoelectric substrate and a first thermally conductive layer arranged over the piezoelectric substrate and interdigital transducer electrode. The first thermally conductive layer is spaced apart from the piezoelectric substrate and interdigital transducer electrode. The surface acoustic wave device also includes a second thermally conductive layer configured to dissipate heat generated by the surface acoustic wave device. The second thermally conductive layer is arranged on an opposing side of the piezoelectric substrate to the interdigital transducer electrode. Related wafer-level packages, radio frequency modules and wireless communication devices are also provided.

An IDT electrode includes first and second busbar electrodes opposed to each other, first and second electrode fingers extending respectively from the first and second busbar electrodes on a piezoelectric substrate. The first busbar electrode and a tip end of the second electrode finger are opposed to each other with a gap therebetween, and bottom surfaces of the first and second busbar electrodes are opposed to each other with a first gap therebetween. The first and second busbar electrodes respectively include portions opposed to each other with a second gap shorter than the first gap therebetween on the top surface side. In a first area located between a first side surface and a second side surface, a second area located between the piezoelectric substrate and the first busbar electrode or the second electrode finger includes a hollow portion.

A surface acoustic wave (SAW) device having a high electromechanical coupling coefficient based on double-layer electrodes and a preparation method thereof. A structure of the SAW device includes a Cu electrode, a piezoelectric film and an Al electrode on a substrate in sequence. A signal terminal of the Cu electrode is opposite to a ground terminal of the Al electrode. A ground terminal of the Cu electrode is opposite to a signal terminal of the Al electrode. Since Sezawa wave mode that is adopted is formed by coupling film thickness vibration and transverse vibration, a longitudinal electric field (in a direction of thickness of a film) and a transverse electric field (in a propagation direction of SAW) are excited through the double-layer electrodes so that the electromechanical coupling coefficient of the SAW device is improved by changing a coupling pattern between the electric fields and the piezoelectric film.

When a current flowing in a series circuit including an equivalent resistance, an equivalent inductor, and an equivalent capacitance in an electric equivalent circuit of a specific resonator in each filter is defined as an acoustic path current, under conditions that a phase of an acoustic path current of a first transmission filter at a side of a common terminal at a frequency within a first pass band is represented as θ1.sub.Tx1, a phase of an acoustic path current of the first transmission filter at the side of the common terminal at a frequency within a second pass band is represented as θ2.sub.Tx1, a phase of an acoustic path current of a second transmission filter at the side of the common terminal at a frequency within the first pass band is represented as θ1.sub.Tx2, and a phase of an acoustic path current of the second transmission filter at the side of the common terminal at a frequency within the second pass band is represented as θ2.sub.Tx2, a multiplexer satisfies a first condition: |(2.Math.θ1.sub.Tx1−θ2.sub.Tx1)−(2.Math.θ1.sub.Tx2−θ2.sub.Tx2)|=180°±90°, or a second condition: |(2.Math.θ2.sub.Tx1−θ1.sub.Tx1)−(2.Math.θ2.sub.Tx2−θ1.sub.Tx2)|=180°±90°.

A ladder-type filter includes a support substrate, a piezoelectric layer provided on the support substrate, a parallel resonator including first electrode fingers provided on the piezoelectric layer and having a first average pitch and a first average duty ratio, a largest first average pitch being equal to or greater than two times a thickness of the piezoelectric layer, a first end of the parallel resonator being coupled to a path between input and output terminals, a second end of the parallel resonator being coupled to a ground, and a series resonator connected in series between the input and output terminals, the series resonator including second electrode fingers provided on the piezoelectric layer and having a second average pitch and a second average duty ratio, a second average duty ratio in at least one series resonator being less than a smallest first average duty ratio.

An acoustic wave device includes a piezoelectric substrate and an IDT electrode. In the IDT electrode, at least one electrode finger includes a first portion and a second portion in an intersection region. The first portion is in direct contact with the piezoelectric substrate. The second portion is on the first portion such that a space in at least a portion of a central portion of the intersection region in the first portion is provided. A thickness of the first portion is smaller than a thickness of a busbar. A sum of the thickness of the first portion in a portion where the second portion is present and a thickness of the second portion is thicker than the thickness of the first portion in a portion where the second portion is not present.

An acoustic wave device, a radio frequency filter and an electronics module are provided. The acoustic wave device comprises a piezoelectric substrate, a temperature compensation layer disposed on the piezoelectric substrate, and an interdigital transducer embedded within the temperature compensation layer and spatially separated from the piezoelectric substrate. The interdigital transducer is configured to generate an acoustic wave in response to an electrical signal. A passivation layer is disposed on the temperature compensation layer. The acoustic wave device can be used in wide passband applications, and has an excellent temperature coefficient, small size, and a clean response.

An acoustic wave filter includes a substrate and a piezoelectric layer over the substrate. First acoustic wave resonators are disposed over the piezoelectric layer and arranged in series along a first branch, and second acoustic wave resonators are disposed over the piezoelectric layer, arranged in parallel, and connected to the first branch and to ground. The first and second acoustic wave resonators include an interdigital transducer electrode interposed between a pair of reflectors. A layer of negative temperature coefficient of frequency dielectric material is disposed over one or more of the second plurality of acoustic wave resonators to control the temperature coefficient of frequency and improve temperature stability of the acoustic wave filter.

An acoustic wave element includes an IDT electrode including a plurality of electrode fingers and exciting a surface acoustic wave, a first substrate including an upper surface on which the IDT electrode is located, the first substrate being configured by a piezoelectric crystal, and a second substrate bonded to a side where a lower surface of the first substrate is located. Either of a first region which continues from the lower surface of the first substrate toward a side where the upper surface is located or a second region which continues from the lower surface of the first substrate toward a side where the second substrate is located is a low resistance region having a resistance value of 5×10.sup.3Ω to 5×10.sup.7Ω.