An electronic device includes a first substrate including a first face on which a common terminal to be coupled to the element is disposed, and a second substrate which has a second face and a third face, and which is arranged so that the second face faces to the first face, wherein the second substrate has a first through hole at a position corresponding to the common terminal, the first through hole penetrating from the second face to the third face, a first through electrode electrically coupled to the common terminal is disposed in the first through hole, and a void is disposed in a part of the first through electrode.

A piezoelectric element includes a support member, a vibrator, a through electrode and a seed layer. The vibrator is disposed on an insulation film of the support member, and includes a piezoelectric film and an electrode coating film electrically connected to the piezoelectric film. The vibrator has a support region and a vibration region. The through electrode is electrically connected to the electrode coating film at the support region, and is disposed in a stacking direction of the support member and the vibrator. Between the piezoelectric film and the insulation film, the seed layer is disposed at a portion of the electrode coating film facing another portion of the electrode coating film connected to the through electrode in the stacking direction. The seed layer is made of material having a lattice constant closer to the piezoelectric film or material easier to cause the piezoelectric film to be self-aligned.

In a piezoelectric device, electrode layers are spaced apart from each other in the direction of the normal thereto. A first piezoelectric layer is interposed between two electrode layers of electrode layers in the direction of the normal. A second piezoelectric layer is provided on an opposite side of the first piezoelectric layer from a base portion. The second piezoelectric layer is interposed between two electrode layers of the electrode layers in the direction of the normal. The half-width of a rocking curve measured by X-ray diffraction for a lattice plane of the first piezoelectric layer substantially parallel to a first main surface is smaller than a half-width for the second piezoelectric layer. The piezoelectric constant of a material defining the first piezoelectric layer is smaller than the piezoelectric constant of a material defining the second piezoelectric layer.

A piezoelectric sensor includes: a lower substrate; a plurality of sensing transistors that are disposed on the lower substrate; a lower electrode that is disposed to cover the plurality of sensing transistors; a piezoelectric material layer that is disposed on the lower electrode; and an upper electrode that is disposed on the piezoelectric material layer. The piezoelectric material layer has a first thickness in a plurality of first areas in which the plurality of sensing transistors are disposed and has a second thickness which is greater than the first thickness in a second area in which the plurality of sensing transistors are not disposed. Accordingly, it is possible to further accurately and finely detect various types of biometric information.

Aspects of this disclosure relate to a boundary acoustic wave device. The boundary acoustic wave device can include two low acoustic impedance layers, an interdigital transducer electrode, piezoelectric material positioned between the interdigital transducer electrode and each of the two low acoustic impedance layers, and two high acoustic impedance substrates. The two low acoustic impedance layers can be positioned between the two high acoustic impedance substrates. Related acoustic wave filters, multiplexers, radio frequency modules, wireless communication devices, and methods are disclosed.

A method for forming a MEMS device is provided. The method includes forming a stack of layers on a base piezoelectric layer. The stack of layers includes a base metal film over the base piezoelectric layer; a first piezoelectric film over the base metal film; and a first metal film having an opening therein over the first piezoelectric film. The method also includes forming a trench in the stack of layers, wherein the trench passes through the opening in the first metal film but does not expose the base metal film; after forming the trench, forming a spacer structure under the first metal film but spaced apart from the base metal film; after forming the spacer structure, deepening the trench to expose the base metal film; and forming a contact in the trench.

A piezoelectric material contains: a first component which is a rhombohedral crystal in a single composition, has a Curie temperature Tc1, and is a lead-free-system composite oxide having a perovskite-type structure; a second component which is a crystal other than a rhombohedral crystal in a single composition, has a Curie temperature Tc2 higher than Tc1, and is a lead-free-system composite oxide having a perovskite-type structure; and a third component which is a rhombohedral crystal in a single composition, has a Curie temperature Tc3 equal to or higher than Tc2, and is a lead-free-system composite oxide that has a perovskite-type structure and is different from the first component. When a molar ratio of the third component to the sum of the first component and the third component is α and α×Tc3+(1−α)×Tc1 is Tc4, |Tc4−Tc2| is 50° C. or lower.

A Microelectromechanical System (MEMS) device which includes a piezoelectric stack on a substrate separated by a dielectric layer is disclosed. The piezoelectric stack includes first and second piezoelectric layers with a first electrode below the first piezoelectric layer and a contact pad and a second electrode between the first and second piezoelectric layers. A first contact extends through the piezoelectric layers and contact pad to the first electrode and a second contact extends through the second piezoelectric layer to the second electrode. The contact pad prevents an interface to form between the first and second piezoelectric layers in the contact opening, thus preventing corrosion of the piezoelectric layers during contact formation process.

A piezoelectric actuator comprises a substantially rectangular parallelepiped piezoelectric element. One outer surface of the piezoelectric element includes a first region, and a second region located such as to project from the first region and to overlap a region corresponding to an active portion in the one outer surface. The second region has a flat surface configured to come into contact with a body to be driven and to generate a frictional force therewith. The flat surface is shorter in a longitudinal direction of the piezoelectric element than in a lateral direction thereof. The flat surface is longer in the longitudinal direction of the piezoelectric element at a lateral center region thereof than at a lateral end region thereof.

An actuator device has an electroactive polymer actuator and an integrated piezoelectric transformer. At least a secondary side of the integrated piezoelectric transformer shares a piezoelectric electroactive polymer layer with the electroactive polymer actuator, so that lower external voltages can be applied to the actuator device. A diode is connected between the secondary side of the integrated piezoelectric transformer and the electroactive polymer actuator.