An acoustic wave device includes an acoustic wave substrate including a first main surface and a second main surface, IDT electrodes provided on the first main surface, and sealing resin covering at least the second main surface of the acoustic wave substrate. A hollow is provided in a region where the IDT electrodes on the first main surface of the acoustic wave substrate is located. The sealing resin has through-holes each extending from a top surface 13B of the sealing resin to the second main surface of the acoustic wave substrate. The acoustic wave substrate is made of silicon or includes a layer made of silicon.

A SAW device includes a mounting substrate including a mounting surface, a SAW chip mounted on the mounting surface, a dummy chip mounted on the mounting surface, and a resin part covering the acoustic wave chip and the dummy chip. The dummy chip includes an insulating dummy substrate, and one or more dummy terminals which are located on a surface of the dummy substrate on the mounting surface side and are bonded to the mounting surface. The dummy chip configures an open end when electrically viewed from the mounting substrate side.

A high-frequency apparatus includes a resin substrate, a first device including a substrate and provided on the resin substrate, and a second device provided adjacent to the first device on the resin substrate. Each of the first device and the second device includes an acoustic wave device. The second device includes a piezoelectric substrate and a functional element provided on the piezoelectric substrate. The substrate of the first device includes Si or a laminated material including Si. The piezoelectric substrate of the second device includes LiTaO.sub.3, LiNbO.sub.3, or a laminated material including LiTaO.sub.3 or LiNbO.sub.3. The resin substrate includes glass.

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 electronic component includes a mounting substrate, and first and second devices each including a functional element. The first device is spaced apart from and faces the mounting substrate. The second device is located on the mounting substrate and faces the first device. A functional element of the first device is located on a first surface facing the second device, in the first device. A functional element of the second device is located on a second surface facing the first device, in the second device.

An acoustic wave device includes a piezoelectric substrate made of LiNbO.sub.3 or LiTaO.sub.3 and including first and second main surfaces that face each other, an IDT electrode provided on the first main surface of the piezoelectric substrate, and a Li.sub.2CO.sub.3 layer provided on the second main surface of the piezoelectric substrate.

A circuit module includes a mounting substrate including a conductor wiring, an elastic wave element provided in or on a main surface of the mounting substrate, an electric element provided in or on the main surface, the electric element being different from the elastic wave element, and an insulating resin portion provided in or on the main surface to cover the elastic wave element and the electric element. The elastic wave element and the electric element are connected to each other by the conductor wiring. A height of the elastic wave element is about 0.28 mm or less, which is less than that of the electric element. The thickness of the resin portion in a region in which the resin portion covers the elastic wave element is greater than the thickness of the resin portion in a region in which the resin portion covers the electric element.

An acoustic wave device includes an acoustic wave element substrate, filter electrodes on a first surface of the acoustic wave element substrate, a first insulator layer covering a second surface of the acoustic wave element substrate, and a second insulator layer laminated on the first insulator layer and sandwiching the first insulator layer between the second insulator layer and the acoustic wave element substrate. The products of propagation speeds of an acoustic wave in those layers and densities of those layers satisfy a predetermined relationship.

An elastic wave device includes an IDT electrode on a second main surface of an element substrate that includes a piezoelectric layer, a support layer on the second main surface and surrounding the IDT electrode, a cover member on the support layer, and routing wiring lines extending from the second main surface of the element substrate onto side surfaces of the element substrate.

An acoustic wave device includes an element substrate having piezoelectricity, a functional electrode on a first main surface of the element substrate, an extended wiring line electrically connected to the functional electrode and extending from the first main surface to a side surface of the element substrate, an external terminal electrically connected to the extended wiring line and on a second main surface of the element substrate, a first resin portion to seal the acoustic wave device, and a second resin portion at least between the extended wiring line on the side surface and the first resin portion. The second resin portion has a lower Young's modulus than the first resin portion.