There is provided a method for manufacturing a niobate-system ferroelectric thin film device, including: a lower electrode film formation step of forming a lower electrode film on a substrate; a niobate-system ferroelectric thin film formation step of forming a niobate-system ferroelectric thin film on the lower electrode film; an etch mask formation step of forming a desired etch mask pattern on the niobate-system ferroelectric thin film; and a ferroelectric thin film etching step of forming a desired fine pattern of the niobate-system ferroelectric thin film by wet etching using an etchant including an aqueous alkaline solution of a chelating agent.

The present invention provides a piezoelectric thin film element having a pair of electrode layers and a piezoelectric thin film sandwiched between the pair of electrode layers, wherein the pair of electrode layers are composed of platinum (Pt), oxide particles are contained in at least one of the electrode layers, and the oxide particles are oxide particles of at least one element constituting the piezoelectric thin film or oxide particles of Pt.

A composite substrate 10 includes a piezoelectric substrate 12 and a support layer 14 bonded to the piezoelectric substrate 12. The support layer 14 is made of a material having no crystalline anisotropy in a bonded surface thereof and has a smaller thickness than the piezoelectric substrate 12. The piezoelectric substrate 12 and the support layer 14 are bonded together with an adhesive layer 16 therebetween. The composite substrate 10 has a total thickness of 180 m or less. The base thickness ratio Tr=t2/(t1+t2) is 0.1 to 0.4, where t1 is the thickness of the piezoelectric substrate 12, and t2 is the thickness of the support layer 14. The thickness t1 is 100 m or less. The thickness t2 is 50 m or less.

A piezoelectric film of the present invention is a piezoelectric film including a perovskite oxide represented by the following formula (P), in which crystal phases of the perovskite oxide include tetragonal crystals and rhombohedral crystals at a ratio that satisfies the following formula (1).

A.sub.1+[(Zr.sub.xTi.sub.1-x).sub.1-aNb.sub.a]O.sub.y(P)

0.70rhombohedral crystals/(rhombohedral crystals+tetragonal crystals)0.95 (1), where, in the formula (P), A is an A-site element primarily containing Pb, and Zr, Ti, and Nb are B-site elements. x is equal to or higher than 0.4 and lower than 1, excluding x of equal to or higher than 0.51 and equal to or lower than 0.53. a is equal to or higher than 0.08.

A capacitor is coupled in parallel with a piezoelectric unit in a sensor. The piezoelectric unit is formed by a film which is sandwiched between a signal electrode and a reference potential electrode. A capacitor is formed by a dielectric film located between the signal electrode and a reference potential electrode. As a result, the capacitance of the sensor element is higher than it would be if the sensor only contained the piezoelectric unit.

The invention provides a lead titanate coating and a preparing method thereof. According to the method, mixed powder is sprayed on the surface of a matrix, and through polarization, the lead titanate coating is acquired. The mixed powder comprises PbTiO.sub.3 powder, PbO powder and Al powder. Lead titanate (PbTiO.sub.3) is a kind of ferroelectric material, and can be used for preparing a piezoelectric sensor. Besides, the PbO powder and the Al powder are added, so that the piezoelectric property of the lead titanate coating can be improved. Since the lead titanate coating prepared by the present invention can be combined with the matrix closely and the intensity of piezoelectric signal is high, it can be widely applied to mechanical parts, such as a piston ring, a cylinder, a gear, and the like, to dynamically monitor the service situations of the parts better.

A compound semiconductor device includes: a flexible part; a first nitride semiconductor layer above a surface of the flexible part, the first nitride semiconductor layer including a first polar plane and a second polar plane intersecting the surface; a second nitride semiconductor layer in contact with the first nitride semiconductor layer on the first polar plane, a lattice constant of the second nitride semiconductor layer being different from that of the first nitride semiconductor layer; a third nitride semiconductor layer in contact with the first nitride semiconductor layer on the second polar plane, a lattice constant of the third nitride semiconductor layer being different from that of the first nitride semiconductor layer; a first ohmic electrode above an interface between the first nitride semiconductor layer and the second nitride semiconductor layer; and a second ohmic electrode above an interface between the first nitride semiconductor layer and the third nitride semiconductor layer.

Provided is a piezoelectric element containing no lead therein and having a satisfactory piezoelectric constant and a small dielectric loss tangent at room temperature (25 C.) In order to attain this, the piezoelectric element includes a substrate, a first electrode, a piezoelectric film, and a second electrode. The piezoelectric film contains barium zirconate titanate, manganese, and trivalent bismuth. The piezoelectric film satisfies 0.02x0.13, where x is a mole ratio of zirconium to the sum of zirconium and titanium. A manganese content is 0.002 moles or more and 0.015 moles or less for 1 mole of barium zirconate titanate, and a bismuth content is 0.00042 moles or more and 0.00850 moles or less for 1 mole of barium zirconate titanate.

A piezoelectric element includes a piezoelectric body that is provided on a substrate and includes multiple sides; a first wiring that is provided from the piezoelectric body to the substrate; and a second wiring that is provided from the piezoelectric body to the substrate. When the piezoelectric element is viewed from a thickness direction of the piezoelectric body, a second side and a fourth side on which the piezoelectric body is superimposed on the first wiring are different from a first side and a third side on which the second wiring is superimposed on the piezoelectric body.

Provided is a piezoelectric element that includes a substrate having a lower electrode, a piezoelectric film, and an upper electrode, in that order, and an insulating film that covers at least a side surface of the piezoelectric film, wherein one of the side surfaces of the piezoelectric film has a plurality of step portions, each of the plurality of step portions has a first side surface and a second side surface, an angle of inclination of the first side surface with respect to an upper surface of the substrate is different from an angle of inclination of the second side surface with respect to the upper surface of the substrate, and an angle between the first side surface and the second side surface is 90 or more.