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.

An acoustic wave device includes a support substrate, a piezoelectric film, and an IDT electrode. When a wavelength defined by an electrode finger pitch of the IDT electrode is λ, a thickness of the piezoelectric film is about 1λ or less. The piezoelectric film has crystal axes. The support substrate includes first and second silicon layers. A plane orientation of the first and second silicon layers is (100), (110), or (111). When angles α1 and β2 are defined between the plane orientations of the first and second silicon layers and the crystal axes, each of the angles α1 and α2 is one of three types of angles of an angle α.sub.100, an angle α.sub.110, and an angle α.sub.111. A type of the angle α1 is different from a type of the angle α2 and/or a value of the angle α1 is different from a value of the angle α2.

A surface acoustic wave device according to the present disclosure includes a support substrate; an intermediate layer laminated on the support substrate; a piezoelectric layer laminated on the intermediate layer; and an IDT electrode formed on the piezoelectric layer, an Euler angle of the support substrate is (−45°±10°, −54°±10°, 180°±30°) and an Euler angle of the piezoelectric layer is (0°±5°, 112.5°±22.5°, 0°±5°) or (0°±5°, −67.5°±22.5°, 0°±5°).

A filter circuit has a cascaded resonator circuit with a first acoustic resonator and a second acoustic resonator connected in series on a printed circuit board (PCB). The admittances as functions of frequency of the first and second acoustic resonators are substantially identical. The filter circuit also has a composite resonator circuit formed by a capacitor connected in parallel with the second acoustic resonator on the PCB. The capacitor improves a steepness of an upper bandpass edge of the filter circuit.

A filter circuit has a cascaded resonator circuit with a first acoustic resonator and a second acoustic resonator connected in series on a printed circuit board (PCB). The admittances as functions of frequency of the first and second acoustic resonators are substantially identical. The filter circuit also has a composite resonator circuit formed by a capacitor connected in parallel with the second acoustic resonator on the PCB. The capacitor improves a steepness of an upper bandpass edge of the filter circuit.

Methods of fabricating resonator and filter devices. A first conductor pattern formed on a front surface of a piezoelectric plate includes a first plurality of contact pads and an interdigital transducer (IDT). The IDT and the piezoelectric plate are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the piezoelectric plate. An acoustic Bragg reflector is between a substrate and a back surface of the piezoelectric plate, the acoustic Bragg reflector configured to reflect the shear primary acoustic mode. A second conductor pattern including a second plurality of contact pads is formed on a back surface of the interposer. The first plurality of contact pads is directly connected to respective contact pads of the second plurality of contact pads. A perimeter of the acoustic resonator chip is sealed to a perimeter of the interposer.

Methods of fabricating resonator and filter devices. A first conductor pattern formed on a front surface of a piezoelectric plate includes a first plurality of contact pads and an interdigital transducer (IDT). The IDT and the piezoelectric plate are configured such that a radio frequency signal applied to the IDT excites a shear primary acoustic mode within the piezoelectric plate. An acoustic Bragg reflector is between a substrate and a back surface of the piezoelectric plate, the acoustic Bragg reflector configured to reflect the shear primary acoustic mode. A second conductor pattern including a second plurality of contact pads is formed on a back surface of the interposer. The first plurality of contact pads is directly connected to respective contact pads of the second plurality of contact pads. A perimeter of the acoustic resonator chip is sealed to a perimeter of the interposer.

The invention relates to a SAW resonator (100) comprising at least: a substrate (102); a layer (108) of piezoelectric material arranged on the substrate; a first attenuation layer (112) arranged between the substrate and the layer of piezoelectric material, and/or, when the substrate comprises at least two different layers (104, 106), a second attenuation layer (114) arranged between the two layers of the substrate; and in which the at least one attenuation layer is/are heterogeneous.

The invention relates to a SAW resonator (100) comprising at least: a substrate (102); a layer (108) of piezoelectric material arranged on the substrate; a first attenuation layer (112) arranged between the substrate and the layer of piezoelectric material, and/or, when the substrate comprises at least two different layers (104, 106), a second attenuation layer (114) arranged between the two layers of the substrate; and in which the at least one attenuation layer is/are heterogeneous.

An elastic wave device includes a piezoelectric substrate made of LiNbO.sub.3, interdigital transducer electrodes on the piezoelectric substrate, and a first dielectric film provided on the piezoelectric substrate and the first dielectric film to cover the IDT electrodes and made of a silicon oxide. The IDT electrodes include a first metal film made of one metal selected from Pt, Cu, Mo, Au, W, and Ta. The Euler angles (ϕ, θ, ψ) of the piezoelectric substrate are (0±5°, −90°≤θ≤−70°, 0°±5°). The metal for the first metal film and the thickness hm/λ (%) match any of the combinations as follows: TABLE-US-00001 Metal for the first metal film Thickness hm/λ (%) of the first metal film Pt 6.5 ≤ hm/λ ≤ 25 Cu  13 ≤ hm/λ ≤ 25 Mo 15.5 ≤ hm/λ ≤ 25  Au 6.5 ≤ hm/λ ≤ 25 W 7.5 ≤ hm/λ ≤ 25 Ta .sup.  7 ≤ hm/λ ≤ 25.