An acoustic wave device includes a piezoelectric body portion, an interdigital transducer electrode connected to a first terminal and a second terminal, and a reflector connected to the second terminal. In the interdigital transducer electrode, in the interdigital transducer electrode, where, of a group of electrode fingers, the electrode finger located at one end in a second direction is a first end electrode finger and the electrode finger located at another end is a second end electrode finger, the first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An outer busbar portion of one of a first busbar and a second busbar, not connected to the first end electrode finger, is located on an inner side in the second direction relative to a center portion, in a first direction, of the first end electrode finger.

An acoustic wave device includes an interdigital transducer electrode connected to first and second terminals, and a reflector connected to the second terminal. In a group of electrode fingers of the interdigital transducer electrode, the electrode fingers at one end and another end in a second direction are respectively first and second end electrode fingers, the first end electrode finger includes a wide portion at a distal end portion. The first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An inner busbar portion of one of first and second busbars not connected to the first end electrode finger, is located on an inner side in the second direction relative to the wide portion of the first end electrode finger so as not to overlap the wide portion of the first end electrode finger in a first direction.

A filter device includes a first filter chip including a first signal terminal and a second filter chip including a second signal terminal that are mounted above a package substrate including a substrate main body. First and second signal electrode pads are provided on a first main surface of the package substrate and are respectively joined to the first and second signal terminals. First and second outer terminals are provided on a second main surface of the substrate main body. The first and second signal electrode pads and the first and second outer terminals are connected to each other with first and second wirings, respectively. The second outer terminal is located at the first signal electrode pad side and the first outer terminal is located at the second signal electrode pad side when seen from above.

An elastic wave device includes a multilayer body, an antenna terminal, a ground terminal, a signal terminal, an IDT electrode, and an insulating film. The multilayer body includes a support substrate and a piezoelectric film disposed on the support substrate. The antenna terminal is disposed on or above the support substrate. The ground terminal is directly disposed on the support substrate. The signal terminal is disposed above the support substrate. The IDT electrode is disposed on the piezoelectric film. The insulating film is disposed between the support substrate and the signal terminal. The multilayer body includes one of a layer made of a high acoustic-velocity material and an acoustic reflection layer.

To provide a method of producing a lithium niobate (LN) substrate which allows treatment conditions regarding a temperature, a time, and the like to be easily managed and in which an in-plane distribution of a volume resistance value is very small, and also variations in volume resistivity are small among substrates machined from the same ingot. A method of producing an LN substrate by using an LN single crystal grown by the Czochralski process, in which a lithium niobate single crystal having a Fe concentration of 50 mass ppm or more and 2000 mass ppm or less in the single crystal and being in a form of an ingot is buried in an Al powder or a mixed powder of Al and Al.sub.2O.sub.3, and heat-treated at a temperature of 450 C. or more and less than 660 C., which is a melting point of aluminum, to produce a lithium niobate single crystal substrate having a volume resistivity controlled to be within a range of 110.sup.8 .Math.cm or more to 210.sup.12 .Math.cm or less.

An acoustic wave device includes a material layer which has Euler angles and an elastic constant at the Euler angles, a piezoelectric body which includes first and second principal surfaces opposing each other, is laminated directly or indirectly on the material layer so that the second principal surface is on the material layer side and has Euler angles, and whose elastic constant at the Euler angles, and an IDT electrode which is disposed on at least one of the first principal surface and the second principal surface of the piezoelectric body. At least one elastic constant among elastic constants C.sub.11 to C.sub.66 of the material layer not equal to 0 and at least one elastic constant among elastic constants C.sub.11 to C.sub.66 of the piezoelectric body not equal to 0 have opposite signs to each other.

Certain aspects of the present disclosure provide a surface acoustic wave (SAW) resonator with piston mode design and electrostatic discharge (ESD) protections. An example electroacoustic device generally includes a piezoelectric material and a first electrode structure disposed above the piezoelectric material. The first electrode structure comprises first electrode fingers arranged within an active region having a first region and a second region. At least one of the first electrode fingers has at least one of a different width or a different height in the first region than in the second region, and the first electrode fingers comprise a first electrode finger that has a width or height in the second region that is less than a corresponding width or height of the at least one of the first electrode fingers in the second region.

An elastic wave element includes a piezoelectric substrate, an IDT electrode including a first comb-shaped electrode and a second comb-shaped electrode, and reflectors. Each of the reflectors includes a first reflective busbar electrode, a second reflective busbar electrode, and reflective electrode fingers. The first comb-shaped electrode includes a first busbar electrode connected to the first reflective busbar electrodes, and first electrode fingers. The second comb-shaped electrode includes a second busbar electrode and second electrode fingers. In in-between areas, in each of which a reflective electrode finger and a first electrode finger adjacent to each other in the elastic-wave propagation direction face each other, connecting electrodes which electrically couple the reflective electrode fingers to the first electrode fingers are provided.

An elastic wave device includes a piezoelectric substrate, a first dielectric film disposed on the piezoelectric substrate, and an IDT electrode laminated on the first dielectric film. The resistivity of the piezoelectric substrate is equal to or lower than the resistivity of the first dielectric film. The resistivity of the first dielectric film is equal to or lower than about 110.sup.14 .Math.cm.

A micro-transfer printable transverse bulk acoustic wave filter comprises a piezoelectric filter element having a top side, a bottom side, a left side, and a right side disposed over a sacrificial portion on a source substrate. A top electrode is in contact with the top side and a bottom electrode is in contact with the bottom side. A left acoustic mirror is in contact with the left side and a right acoustic mirror is in contact with the right side. The thickness of the transverse bulk acoustic wave filter is substantially less than its length or width and its length can be greater than its width. The transverse bulk acoustic wave filter can be disposed on, and electrically connected to, a semiconductor substrate comprising an electronic circuit to control the transverse bulk acoustic wave filter and form a composite heterogeneous device that can be micro-transfer printed.