Methods for forming a film bulk acoustic resonator (FBAR) are provided. In the method, formation of several mutually overlapped and hence connected sacrificial material layers above and under a resonator sheet facilitates the removal of the sacrificial material layers. Cavities left after the removal overlap at a polygonal area with non-parallel sides. This reduces the likelihood of boundary reflections of transverse parasitic waves causing standing wave resonance in the FBAR, thereby enhancing its performance in parasitic wave crosstalk. Further, according to the disclosure, the FBAR is enabled to be integrated with CMOS circuitry and hence exhibits higher reliability.

A preparation method tor a piezoelectric fiber is provided including a piezoelectric functional layer and an insulating layer coated on the piezoelectric functional layer. The piezoelectric functional layer includes a piezoelectric composite layer of a spiral winding structure, and the piezoelectric composite layer includes a first piezoelectric layer, a conductive layer and a second piezoelectric layer that are sequentially stacked. The preparation method piezoelectric composite layer in a direction perpendicular to the winding axis to form the piezoelectric functional layer, wherein turns of winding the piezoelectric composite layer are greater than 5, coating the piezoelectric functional layer with the insulating layer, and vacuum heating to consolidate, to prepare a preform rod.

A preparation method tor a piezoelectric fiber is provided including a piezoelectric functional layer and an insulating layer coated on the piezoelectric functional layer. The piezoelectric functional layer includes a piezoelectric composite layer of a spiral winding structure, and the piezoelectric composite layer includes a first piezoelectric layer, a conductive layer and a second piezoelectric layer that are sequentially stacked. The preparation method piezoelectric composite layer in a direction perpendicular to the winding axis to form the piezoelectric functional layer, wherein turns of winding the piezoelectric composite layer are greater than 5, coating the piezoelectric functional layer with the insulating layer, and vacuum heating to consolidate, to prepare a preform rod.

Provided are a laminated piezoelectric element and an electroacoustic transducer capable of obtaining high piezoelectric characteristics and easily ensuring an electric contact to an electrode layer. A plurality of layers of piezoelectric films, each of which is formed by laminating a first protective layer, a first electrode layer, a piezoelectric layer, a second electrode layer, and a second protective layer in this order, are laminated. Each of the piezoelectric layers is polarized in a thickness direction. In each of the piezoelectric films, the first electrode is disposed on an upstream side in a polarization direction of the piezoelectric layer, and the second electrode is disposed on a downstream side. Each of the plurality of piezoelectric films has a cemented portion which is cemented to an adjacent piezoelectric film and a protruding portion which is not cemented to the adjacent piezoelectric film and in which at least the first electrode layer and the first protective layer or the second electrode layer and the second protective layer protrude from the cemented portion toward the outside in a plane direction. At the protruding portion of each of the piezoelectric films, at least one of a first contact, to which the first electrode layers of the piezoelectric films are electrically connected to each other, or a second contact, to which the second electrode layers of the piezoelectric films are electrically connected to each other, is formed.

A wafer level ultrasonic chip module includes a substrate, a composite layer, a conducting material, and a base material. The substrate has a through slot that passes through an upper surface of the substrate and a lower surface of the substrate. The composite layer includes an ultrasonic body and a protective layer. A lower surface of the ultrasonic body is exposed from the through slot. The protective layer covers the ultrasonic body and a partial upper surface of the substrate. The protective layer has an opening, from which a partial upper surface of the ultrasonic body is exposed. The conducting material is in contact with the upper surface of the ultrasonic body. The base material covers the through slot, such that a space is formed among the through slot, the lower surface of the ultrasonic body and an upper surface of the base material.

A multi-level piezoelectric actuator is manufactured using wafer level processing. Two PZT wafers are formed and separately metallized for electrodes. The metallization on the second wafer is patterned, and holes that will become electrical vias are formed in the second wafer. The wafers are then stacked and sintered, then the devices are poled as a group and then singulated to form nearly complete individual PZT actuators. Conductive epoxy is added into the holes at the product placement step in order to both adhere the actuator within its environment and to complete the electrical via thus completing the device. Alternatively: the first wafer is metallized; then the second wafer having holes therethrough but no metallization is stacked and sintered to the first wafer; and patterned metallization is applied to the second wafer to both form electrodes and to complete the vias. The devices are then poled as a group, and singulated.

A multilayer piezoelectric ceramic is constituted by: piezoelectric ceramic layers which do not contain lead as a constituent element, have a perovskite compound expressed by the composition formula Li.sub.xNa.sub.yK.sub.1−x−yNbO.sub.3 (where 0.02<x≤0.1, 0.02<x+y≤1) as the primary component, and contain 0.2 to 3.0 mol of Li relative to 100 mol of the primary component; and internal electrode layers which are constituted by a metal that contains silver by 80 percent by mass or more; wherein the multilayer piezoelectric ceramic is such that Li compounds other than the primary component are localized therein. The multilayer piezoelectric element can offer excellent insulating property.

In a non-limiting embodiment, a device may include a substrate, and a hybrid active structure disposed over the substrate. The hybrid active structure may include an anchor region and a free region. The hybrid active structure may be connected to the substrate at least at the anchor region. The anchor region may include at least a segment of a piezoelectric stack portion. The piezoelectric stack portion may include a first electrode layer, a piezoelectric layer over the first electrode layer, and a second electrode layer over the piezoelectric layer. The free region may include at least a segment of a mechanical portion. The piezoelectric stack portion may overlap the mechanical portion at edges of the piezoelectric stack portion.

A multilayer structure and a piezoelectric device using the same, which have satisfactory crystal orientation even in the submicron region of the thickness of a piezoelectric layer, are provided. The multilayer structure includes a first wurtzite thin film, a first hexagonal metal layer, a first electrode layer, a second hexagonal metal layer, and a second wurtzite thin film stacked in this order. The first electrode layer is formed of a metallic material having an acoustic impedance higher than that of the second wurtzite thin film.

A multilayer structure and a piezoelectric device using the same, which have satisfactory crystal orientation even in the submicron region of the thickness of a piezoelectric layer, are provided. The multilayer structure includes a first wurtzite thin film, a first hexagonal metal layer, a first electrode layer, a second hexagonal metal layer, and a second wurtzite thin film stacked in this order. The first electrode layer is formed of a metallic material having an acoustic impedance higher than that of the second wurtzite thin film.