Examples are directed to suppressing crack development in a surface acoustic wave (SAW) element including a double-layered IDT electrode. In one example the SAW element includes a piezoelectric substrate, a comb-shaped electrode formed on a top surface of the piezoelectric substrate, and an insulation layer formed on the top surface of the piezoelectric substrate to cover the comb-shaped electrode. The comb-shaped electrode includes a plurality of electrode fingers each having a first metal layer of a first metal formed on the top surface of the piezoelectric substrate, a second metal layer of a second metal formed on the first metal layer, and a second protective film at least partially covering the second metal layer, the second metal layer being covered by the second protective film and the first metal layer.

An elastic wave device including a substrate, an interdigital transducer (IDT) electrode provided on an upper surface of the substrate, a first wiring electrode provided on the upper surface of the substrate and connected to the IDT electrode, a dielectric film that does not cover a first region of the first wiring electrode but covers a second region of the first wiring electrode above the substrate, the first wiring electrode including a cutout in the second region, and a second wiring electrode that covers an upper surface of the first wiring electrode in the first region and an upper surface of the dielectric film in the second region above the substrate.

An acoustic wave device includes a silicon support substrate, a silicon nitride film on the support substrate, a silicon oxide film on the silicon nitride film, a piezoelectric layer on the silicon oxide film and using Y-cut X-SAW propagation lithium tantalate, and an IDT electrode on the piezoelectric layer. A film thickness of the piezoelectric layer is equal to or less than about 1, Euler angles of the piezoelectric layer are (05, , 05) or (05, , 1805), in the Euler angles of the piezoelectric layer is about 95.5<117.5 or about 84.5<62.5, and a relationship between in the Euler angles of the piezoelectric layer and a film thickness of the silicon nitride film is a combination shown in Table 1 or Table 2.

In an acoustic wave device, an unnecessary high-order transverse mode wave is suppressed. The acoustic wave device includes a piezoelectric substrate, at least one pair of interdigital transducer (IDT) electrodes formed on the piezoelectric substrate, and a dielectric film which covers at least a part of the piezoelectric substrate and the IDT electrodes. The IDT electrodes each have a plurality of electrode fingers interleaved with each other. An acoustic velocity of an acoustic wave in the area in which the electrode fingers are interleaved with each other is greater than an acoustic velocity of an acoustic wave in an edge area including end portions of the electrode fingers.

An elastic wave device including a substrate, an interdigital transducer (IDT) electrode provided on an upper surface of the substrate, a first wiring electrode provided on the upper surface of the substrate and connected to the IDT electrode, a dielectric film that does not cover a first region of the first wiring electrode but covers a second region of the first wiring electrode above the substrate, the first wiring electrode including a cutout in the second region, and a second wiring electrode that covers an upper surface of the first wiring electrode in the first region and an upper surface of the dielectric film in the second region above the substrate.

An elastic wave device includes a piezoelectric substrate, functional electrodes on the piezoelectric substrate, a support layer on the piezoelectric substrate with a frame shape surrounding the functional electrodes, a cover member on the support layer to seal an opening of the support layer, the cover member including a first main surface facing the support layer, and a second main surface opposite to the first main surface. Recesses are located in the cover member and are open to the second main surface. Via holes extend through the support layer and to bottom surfaces of the recesses of the cover member, the via holes each including an opening that is open to the bottom surface. The area of the opening of each of the via holes is not more than the area of the bottom surface of the corresponding recess of the cover member. First via conductor portions are provided in the via holes and second via conductor portions are provided in the recesses of the cover member.

An elastic wave device including a sealing structure. Examples of the elastic wave device include a piezoelectric substrate, an IDT electrode provided on the substrate, a first wiring electrode provided on the substrate adjacent the IDT electrode, a second wiring electrode provided on the first wiring electrode, and a dielectric sealing structure that extends over and seals an excitation space above the IDT electrode in which the IDT electrode excites the elastic wave. The second wiring electrode includes a protrusion formed on its outer periphery and extending beyond the first wiring electrode into the excitation space. The first and/or second wiring electrodes are electrically connected to the IDT electrode. The dielectric sealing structure includes a sealing wall provided on the second wiring electrode, the sealing wall being spaced apart from the IDT electrode by the protrusion and having a side surface that defines a side edge of the excitation space.

An acoustic wave device comprises an IDT electrode disposed above an upper surface of a piezoelectric substrate and includes a plurality of electrode fingers configured to excite a main acoustic wave. A first dielectric film made of an oxide is disposed above the upper surface of the piezoelectric substrate and covers the plurality of electrode fingers. A second dielectric film made of non-oxide is disposed between the first dielectric film and each of the plurality of electrode fingers. A third dielectric film is disposed between the piezoelectric substrate and the plurality of electrode fingers. A speed of a transverse wave propagating through the third dielectric film is greater than a speed of the main acoustic wave propagating through the piezoelectric substrate. The third dielectric film contacts the first dielectric film between adjacent electrode fingers of the plurality of electrode fingers.

An electronic device includes an insulation material layer provided on a first main surface of a piezoelectric substrate and surrounding a functional element, and a protective layer provided on the insulation material layer. The piezoelectric substrate and the insulation material layer define a hollow portion accommodating the functional element. The protective layer includes a first portion above the hollow portion, a second portion adjacent to the first portion at one end of the second portion, and a third portion adjacent to the second portion at another end of the second portion. A distance between the first main surface and a surface of the protective layer in the thickness direction is greatest at a location where the second portion is adjacent to or in a vicinity of the first portion, and the distance is shortest at a location where the second portion is adjacent to or in a vicinity of the third portion.

A production method for a surface acoustic wave device comprises the following steps: a step of providing a piezoelectric substrate comprising a transducer arranged on the main front face; a step of depositing a dielectric encapsulation layer on the main front face of the piezoelectric substrate and on the transducer; and a step of assembling the dielectric encapsulation layer with the main front face of a support substrate having a coefficient of thermal expansion less than that of the piezoelectric substrate. In additional embodiments, a surface acoustic wave device comprises a layer of piezoelectric material equipped with a transducer on a main front face, arranged on a substrate support of which the coefficient of thermal expansion is less than that of the piezoelectric material. The transducer is arranged in a dielectric encapsulation layer, between the layer of piezoelectric material and the support substrate.