A method for manufacturing a piezoelectric bulk acoustic wave element by forming a sacrificial layer on a part of a primary surface of a substrate. A piezoelectric film sandwiched between a pair of electrodes is formed on the primary surface of the substrate so as to cover the sacrificial layer, the piezoelectric film being formed from scandium-containing aluminum nitride having a scandium atomic concentration with respect to the total number of scandium atoms and aluminum atoms of more than 24 atomic percent. An etching step of removing the sacrificial layer by etching is performed. Prior to the etching step, a protective film formed from aluminum nitride or scandium-containing aluminum nitride having a lower scandium atomic concentration than that of the piezoelectric film is provided so as to cover at least a part of a portion of the piezoelectric film located in a region in which the sacrificial layer is provided.

A bulk acoustic wave filter device and method thereof includes a first layer forming an air gap together with a substrate, a lower electrode disposed over the first layer, a piezoelectric layer disposed to cover a portion of the lower electrode, an upper electrode disposed over the piezoelectric layer, a frame layer disposed below the upper electrode, and a lower electrode reinforcing layer disposed on the lower electrode, other than portions in which the piezoelectric layer is disposed. The lower electrode reinforcing layer is formed by separating the lower electrode reinforcing layer from the upper electrode or the frame layer upon one of the upper electrode and the frame layer being formed.

A bulk acoustic wave filter device includes a substrate, a lower electrode on the substrate, a piezoelectric layer covering at least a portion of the lower electrode, and an upper electrode covering at least a portion of the piezoelectric layer. The upper electrode has a density reduction layer disposed on at least a portion thereof, except a central portion of a resonance region of the bulk acoustic wave filter device that deforms and vibrates with the piezoelectric layer during activation of the piezoelectric layer. The density reduction layer has a density lower than a density of other portions of the upper electrode.

An acoustic resonator including a substrate, an active vibration region including, sequentially stacked on the substrate, a lower electrode, a piezoelectric layer, and an upper electrode, and a horizontal resonance suppressing part formed from and disposed in the piezoelectric layer, the horizontal resonance suppressing part having piezoelectric physical properties that are different from piezoelectric physical properties of the piezoelectric layer.

A bulk acoustic resonator, related devices including a resonator assembly, a filter, and an electronic device, and a method for manufacturing a bulk acoustic wave resonator are provided. The bulk acoustic resonator includes a substrate and an acoustic reflection component, a first electrode, a piezoelectric layer, and a second electrode that are sequentially stacked on a surface of the substrate. A first gap is provided between the first electrode and the piezoelectric layer. A second gap is provided between the piezoelectric layer and a second electrode connection part of the second electrode in addition to a part of the second electrode located within the effective resonance region. The first gap interlaces and overlaps with the second gap in a direction perpendicular to a plane where the substrate is located.

The present application provides a bulk acoustic resonator and a preparation method thereof, and a filter. The bulk acoustic resonator includes: a substrate, wherein the substrate includes a first semiconductor layer, an insulating layer and a second semiconductor layer, which are stacked in sequence; the surface of the second semiconductor layer is etched to form a groove, and the groove penetrates through the second semiconductor layer; and a protection part is formed in the groove, and a vertical section of the groove has a smooth contour.

A bulk acoustic wave resonator and method for manufacturing the same, the bulk acoustic wave resonator includes: a piezoelectric layer; a first electrode layer, a carrier structure, and first and second conductive connectors disposed on a first side of the piezoelectric layer, and a second electrode layer, an interconnection pad and a cover structure disposed on a second side of the piezoelectric layer, wherein the first electrode layer includes a first electrode and an additional electrode electrically isolated from each other; the second electrode layer includes a second electrode; the interconnection pad is electrically connected to the second electrode and the additional electrode; a first cavity is disposed between the carrier structure and the piezoelectric layer; the first conductive connector is electrically connected to the first electrode, the second conductive connector is electrically connected to the second electrode through the additional electrode and the interconnection pad.

Filter devices are disclosed. A filter device includes a piezoelectric plate comprising a supported portion, a first diaphragm, and a second diaphragm. The supported portion is attached to a substrate and the first and second diaphragms spans respective cavities in the substrate. A first interdigital transducer (IDT) has interleaved fingers on the first diaphragm. A second interdigital transducer (IDT) has interleaved fingers on the second diaphragm. A first dielectric layer is between the interleaved fingers of the first IDT, and a second dielectric layer is between the interleaved fingers of the second IDT. A thickness of the first dielectric layer is greater than a thickness of the second dielectric layer. The piezoelectric plate and the first and second IDTs are configured such that radio frequency signals applied to first and second IDTs excite primary shear acoustic modes in the respective diaphragms.

Disclosed are polarization-inverted higher-order plate-mode resonators and methods for making the same. In an aspect, a plate-mode resonator includes a first piezoelectric layer having a first crystal orientation specified by a first set of Euler angles .sub.1, .sub.1, and .sub.1, a dielectric layer disposed on a top surface of the first piezoelectric layer, a second piezoelectric layer, disposed on a top surface of the dielectric layer, having a second crystal orientation specified by a second set of Euler angles .sub.2, .sub.2, and .sub.2, wherein az is approximately equal to .sub.1, wherein a difference between .sub.2 and .sub.1 is approximately 180 degrees, and wherein .sub.2 is approximately equal to .sub.1, and a metallization structure disposed on a top surface of the second piezoelectric layer, the metallization structure comprising at least one interdigital transducer.

A method of forming a film can include heating a CVD reactor chamber containing a substrate to a temperature range between about 750 degrees Centigrade and about 950 degrees Centigrade, providing a first precursor comprising Al to the CVD reactor chamber in the temperature range, providing a second precursor comprising Sc to the CVD reactor chamber in the temperature range, providing a third precursor comprising nitrogen to the CVD reactor chamber in the temperature range, and forming the film comprising ScAlN on the substrate.