There are provided a piezoelectric film-attached substrate and piezoelectric element, which include, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide containing lead as a main component of an A site, and a buffer layer, where the buffer layer contains a metal oxide represented by M.sub.dN.sub.1-dO.sub.e. Here, M consists of one or more metal elements substitutable for the A site of the perovskite-type oxide and has an electronegativity of less than 0.95. In a case of 0<d<1 and in a case where the electronegativity is denoted by X, 1.41X−1.05≤d≤A1.Math.exp(−X/t1)+y0, where A1=1.68×10.sup.12, t1=0.0306, and y0=0.59958.

There are provided a piezoelectric film-attached substrate and piezoelectric element, which include, on a substrate in the following order, a lower electrode layer, a piezoelectric film containing a perovskite-type oxide containing lead as a main component of an A site, and a buffer layer, where the buffer layer contains a metal oxide represented by M.sub.dN.sub.1-dO.sub.e. Here, M consists of one or more metal elements substitutable for the A site of the perovskite-type oxide and has an electronegativity of less than 0.95. In a case of 0<d<1 and in a case where the electronegativity is denoted by X, 1.41X−1.05≤d≤A1.Math.exp(−X/t1)+y0, where A1=1.68×10.sup.12, t1=0.0306, and y0=0.59958.

Provided is a piezoelectric material filler including alkali niobate compound particles having a ratio (K/(Na+K)) of the number of moles of potassium to the total number of moles of sodium and potassium of 0.460 to 0.495 in terms of atoms and a ratio ((Li+Na+K)/Nb) of the total number of moles of alkali metal elements to the number of moles of niobium of 0.995 to 1.005 in terms of atoms. The present invention can provide a piezoelectric material filler having excellent piezoelectric properties, and a composite piezoelectric material including the piezoelectric material filler and a polymer matrix.

There is provided a laminated substrate having a piezoelectric film, including: a substrate; and a piezoelectric film provided on the substrate interposing a base film, wherein the piezoelectric film has an alkali niobium oxide based perovskite structure represented by a composition formula of (K.sub.1-xNa.sub.x)NbO.sub.3 (0<x<1) and preferentially oriented in (001) plane direction, and a sound speed of the piezoelectric film is 5100 m/s or more.

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.

An actuator has a plurality of pairs of a flexible electrode having flexibility, and a base electrode having an opposed face that is opposed to the flexible electrode and is covered with an insulating layer. The flexible electrode is configured to deform to get closer to the opposed face when a voltage is applied to the flexible electrode and the base electrode. Each of the pairs is located on the same axis, and adjacent ones of the pairs are connected to each other. The axis intersects with the opposed face of the base electrode of each of the pairs. The base electrode of each of the pairs is divided into a plurality of electrode portions insulated from each other, and the voltage is individually applied to the electrode portions.

An actuator has a flexible electrode having flexibility, and a base electrode having an opposed face that is opposed to the flexible electrode and is covered with an insulating layer. The flexible electrode deforms to get closer to the opposed face when a voltage is applied to the flexible electrode and the base electrode. The flexible electrode is a rotating body placed on the opposed face. The base electrode is divided into a plurality of electrode portions insulated from each other. The electrode portions are arranged along a predetermined direction. The flexible electrode moves in the predetermined direction relative to the base electrode, while rotating on the opposed face, when the voltage is sequentially applied to the electrode portions in the predetermined direction.

An acoustic wave device has a substrate, an optional functional layer disposed over at least a portion of the substrate, a piezoelectric layer disposed over at least a portion of the functional layer and/or substrate, and an interdigital transducer electrode disposed on the piezoelectric layer. The piezoelectric layer has an outer edge spaced inward of an outer edge of the substrate, the outer edge of the piezoelectric layer being tapered at an angle relative to a surface of the substrate to thereby reduce an acoustic reflection magnitude at said outer edge of the piezoelectric layer.

A piezoelectric film on a substrate is provided comprising an aluminum nitride (AlN) layer, and a Al.sub.1-x(J).sub.xN compound layer comprising a graded section with a lower (J) composition, x, adjacent to the AlN layer and a higher (J) composition, x, located away from the AlN layer, the said (J) being a singular element or a binary compound. A method for forming such a piezoelectric film is also provided. A surface acoustic wave resonator comprising such a piezoelectric film, a surface acoustic wave filter comprising such a piezoelectric film, a bulk acoustic wave resonator comprising such a piezoelectric film, and a bulk acoustic wave filter comprising such a piezoelectric film are also provided.

A piezoelectric film on a substrate is provided comprising an aluminum nitride (AlN) layer, and a Al.sub.1-x(J).sub.xN compound layer comprising a graded section with a lower (J) composition, x, adjacent to the AlN layer and a higher (J) composition, x, located away from the AlN layer, the said (J) being a singular element or a binary compound. A method for forming such a piezoelectric film is also provided. A surface acoustic wave resonator comprising such a piezoelectric film, a surface acoustic wave filter comprising such a piezoelectric film, a bulk acoustic wave resonator comprising such a piezoelectric film, and a bulk acoustic wave filter comprising such a piezoelectric film are also provided.