An electronic component includes: a first substrate; a second substrate that includes a functional element formed on a lower surface of the second substrate, the second substrate being mounted on the first substrate so that the functional element faces an upper surface of the first substrate across an air gap; and an insulating film that is located on the upper surface of the first substrate, overlaps with at least a part of the functional element in plan view, faces the functional element across the air gap, and has a film thickness that is more than half of a distance between a lower surface of the functional element and the upper surface of the first substrate.

A surface acoustic wave device includes a piezoelectric substrate, an IDT electrode that is provided on the piezoelectric substrate and includes combtooth-shaped electrode fingers, and a wiring electrode that is connected to the IDT electrode. A line width of the electrode fingers at a lower edge thereof and a line width of the electrode fingers at an upper edge thereof in a cross section of the electrode fingers that is perpendicular or substantially perpendicular to a longitudinal direction of the electrode fingers is smaller than a maximum line width of the electrode fingers.

An electronic component includes a functional electrode provided on a first substrate that has a rectangular or substantially rectangular plate shape and a support layer including resin that surrounds the functional electrode. A cover member closes an opening of the support layer. A via conductor penetrating the support layer is provided in at least one corner portion of the support layer. A resin reinforcing portion having the same height or substantially the same height as the support layer is provided in an outer side portion of the corner portion provided with the via conductor.

A multiplexer includes elastic wave filters with different pass bands, a common terminal to which an inductance element is serially connected in a connection path between an antenna element and the common terminal; and an inductance element. Among the elastic wave filters, a reception input terminal of a first reception filter is connected to the common terminal via the inductance element and is connected to a parallel resonator. Transmission output terminals of transmission filters and a reception input terminal of a second reception filter are connected to the common terminal, are connected to series resonators, and are not connected to parallel resonators.

An acoustic wave device includes: a first substrate that has a first surface and a second surface, the second surface being an opposite surface of the first substrate from the first surface; an acoustic wave element that is located on the first surface; a wiring portion that electrically connects the acoustic wave element and a metal portion through a through hole, the metal portion being located on the second surface, the through hole penetrating through the first substrate; and a sealing portion that is located on the first surface so as to surround the acoustic wave element, overlaps with at least a part of the through hole in plan view, and seals the acoustic wave element in an air gap.

A composite filter device for use in carrier aggregation includes a first bandpass filter connected to an antenna common terminal and including a first pass band, and a second bandpass filter including a second pass band of a higher frequency than the first pass band. The first bandpass filter includes an LiNbO.sub.3 substrate, an IDT electrode which is provided on the LiNbO.sub.3 substrate and defines the first bandpass filter, and a dielectric film which covers the IDT electrode and includes silicon oxide as a main component. The first bandpass filter is defined by at least one elastic wave resonator, and a Rayleigh wave propagating in the LiNbO.sub.3 substrate is used and an acoustic velocity of a Sezawa wave in the elastic wave resonator is equal to or higher than about 4643.2 m/sec.

A multiplexer includes elastic wave filters with different pass bands, a common terminal to which an inductance element is serially connected in a connection path between an antenna element and the common terminal; and an inductance element. Among the elastic wave filters, a reception input terminal of a first reception filter is connected to the common terminal via the inductance element and is connected to a parallel resonator. Transmission output terminals of transmission filters and a reception input terminal of a second reception filter are connected to the common terminal, are connected to series resonators, and are not connected to parallel resonators.

Trim layers that are configured to adjust one or more operating parameters for surface acoustic wave (SAW) devices are disclosed. A SAW device may include an interdigital transducer (IDT) and a piezoelectric material that are configured to generate an acoustic wave and a trim layer that has an acoustic velocity and a density that correspond to a velocity of the acoustic wave. In this manner, the trim layer may be configured to adjust an electromechanical coupling of the SAW device without significantly impacting a resonance frequency of the SAW device. The SAW device may also include an additional trim layer that is configured to adjust a coupling percentage and the resonance frequency of the SAW device. A SAW device may include a trim layer that is configured to adjust certain operating parameters by greater amounts than other operating parameters.

The present application describes embodiments of a zero-power radio-frequency identification (RFID) sensor chip based on a combination of a surface acoustic wave (SAW) transducer and two-dimensional electron gas (2DEG) or two-dimensional holegas (2DHG) conducting structure, and its use as an ultrasensitive microphone for material and structure sensing. The SAW RFID sensor contains a piezoelectric substrate, on which a multilayer heterojunction structure is deposited. The heterojunction structure comprises at least two layers, a buffer layer and a barrier layer, wherein both layers are grown from III-V single-crystalline or polycrystalline semiconductor materials, such as Ga N/Al Ga N. Interdigitated transducers (IDTs) transducing SAWs are installed on top of the barrier layer. A conducting channel comprising a two-dimensional electron gas (2DEG), in case of two-layers configuration, or a two-dimensional hole gas (2DHG), in case of three-layers configuration, is formed at the interface between the buffer and barrier layers and provides electron or hole current in the system between the non-ohmic (capacitively-coupled) source and drain contacts connected to the formed channel.

In an acoustic wave device, an IDT electrode is located on a piezoelectric layer. A high-acoustic-velocity member is positioned on an opposite side of the piezoelectric layer from the IDT electrode. An acoustic velocity of a bulk wave propagating through the high-acoustic-velocity member is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric layer. A low-acoustic-velocity film is provided between the high-acoustic-velocity member and the piezoelectric layer. An acoustic velocity of a bulk wave propagating through the low-acoustic-velocity film is lower than the acoustic velocity of the bulk wave propagating through the piezoelectric layer. A dielectric film is located on the piezoelectric layer so as to cover the IDT electrode. In the acoustic wave device, a Young's modulus of the dielectric film is larger than a Young's modulus of the low-acoustic-velocity film.