An acoustic wave filter includes series arm resonators each including an IDT electrode on a piezoelectric substrate. Resonant frequencies of the series arm resonators are positioned within the pass band of the acoustic wave filter. The IDT electrode includes a pair of comb-shaped electrodes. Each of the comb-shaped electrodes includes electrode fingers and a busbar electrode. The electrode fingers extend in a direction intersecting a propagation direction of acoustic waves and are parallel with each other. One end of an electrode finger and one end of another electrode finger are connected with each other by the busbar electrode. The IDT electrode of the series arm resonator with the lowest anti-resonant frequency includes two or more withdrawal-weighted floating electrodes without any of the electrode fingers of one of the comb-shaped electrodes interposed therebetween.

An acoustic wave filter includes a piezoelectric substrate, first and second input-output terminals, and a longitudinally coupled resonator unit in a path connecting the first and second input-output terminals to each other, and the resonator unit includes five or more interdigital transducer electrodes aligned in an acoustic wave propagation direction, the IDT electrodes include a center IDT electrode at the center in the propagation direction and first and second IDT electrodes at symmetric or substantially symmetric positions in the propagation direction with respect to the center IDT electrode, each of the first and second IDT electrodes includes a main pitch portion and a pair of narrow-pitch portions provided between the main pitch portion and both ends of the IDT electrode in the propagation direction, and the first and second IDT electrodes differ from each other in the number of electrode fingers of the main pitch portion.

An acoustic wave device includes a high-acoustic-velocity film, a piezoelectric layer provided directly or indirectly on the high-acoustic-velocity film, an IDT electrode provided on the piezoelectric layer, and a dielectric film provided on the piezoelectric layer to cover the IDT electrode. An acoustic velocity of bulk waves propagating through the high-acoustic-velocity film is higher than an acoustic velocity of acoustic waves propagating through the piezoelectric layer. The dielectric film includes a material including hydrogen atoms.

A surface acoustic wave (SAW) filter device includes: a first layer disposed on a substrate; an inter-digital transducer (IDT) electrode layer disposed on the first layer; a second layer covering the IDT electrode layer and the first layer; and an overlay layer covering the second layer, wherein the first layer includes any one or any combination of any two or more of a metal layer, a metal oxide layer, and an oxide layer.

An electronic device includes a support layer is provided on a piezoelectric substrate and surrounds a functional element. A cover layer is located above the support layer, and faces the piezoelectric substrate. A protective layer seals the support layer and the cover layer. The support layer is provided on at least the outer periphery of the piezoelectric substrate, and defines a hollow portion within the outer periphery of the piezoelectric substrate. The protective layer includes a first portion above the hollow portion, a second portion above the support layer, and a curved surface that is convex in an opposite direction from the piezoelectric substrate.

An elastic wave device includes an IDT electrode and an insulating film on a piezoelectric substrate. Above an intersection region of the IDT electrode, when one end in an elastic-wave propagation direction is a first end portion and the other end in the elastic-wave propagation direction is a second end portion, the thickness of the insulating film is decreased or increased towards a center in the elastic-wave propagation direction from the first end portion and the second end portion.

A surface acoustic wave (SAW) device including a substrate is provided. Multiple surface acoustic wave elements are disposed on the substrate. A conductive surrounding structure includes: a wall part, disposed on the substrate and surrounding the surface acoustic wave elements; and a lateral layer part, disposed on the wall part. The lateral layer part has an opening above the surface acoustic wave elements. A cap layer covers the lateral layer part and closes the opening.

A surface acoustic wave filter includes resonators, wherein one of the resonator includes four or more regions with different pitches of electrode fingers, the pitch of electrode fingers in each of the four or more regions is constant, the pitch of electrode fingers in first regions, among the four or more regions, disposed at both ends of the resonator in a surface acoustic wave propagation direction is smaller than the pitch of electrode fingers in the regions other than the first regions, and the pitch of electrode fingers in a second region adjacent to the first region and the pitch of electrode fingers in a third region adjacent to the first region are different from each other.

A surface acoustic wave device comprises a substrate and an interdigital transducer (IDT) electrode disposed on the substrate. The IDT electrode includes a lower electrode layer having a lower surface in contact with an upper surface of the substrate and an upper electrode layer having a lower surface defining a base in contact with an upper surface of the lower electrode layer. Side surfaces of the lower electrode layer are substantially perpendicular to the upper surface of the substrate. Side surfaces of the upper electrode layer are disposed at an acute angle relative to the upper surface of the substrate.

An elastic wave device includes a substrate, an IDT electrode, a wire, an electrically insulating film, and an identification marking. The substrate has piezoelectricity. The IDT electrode is provided on the substrate and includes a pair of comb-shaped electrodes facing each other. The wire is provided on the substrate and connected to the IDT electrode. The electrically insulating film is provided at least on the IDT electrode and the wire. The identification marking is defined by an uneven portion of a surface of the electrically insulating film. The identification marking does not to overlap the IDT electrode in plan view of the substrate.