Abstract: A method for manufacturing a composite substrate that prevents undesirable effects of etching a thin film includes a pattern forming step, an ion implanting step, a bonding step, and a separation step. In the pattern forming step, a pattern region and a reverse pattern region are formed on a principal surface of a functional material substrate. In the ion implanting step, by implanting ions into the functional material substrate, a separation layer is formed inside at a certain distance from the surface of each of the pattern region and the reverse pattern region. In the bonding step, the functional material substrate at the pattern region is bonded to a supporting substrate. In the separation step, the pattern region is separated from the functional material substrate, and the reverse pattern region is made to fall off.

Abstract: A piezoelectric device includes IDT electrodes and solves various problems resulting from the IDT electrodes. The piezoelectric device has a configuration in which a piezoelectric thin-film and a support are bonded together such that the piezoelectric thin-film is supported by the support. IDT electrodes and interconnect electrodes are provided on a surface of the piezoelectric thin-film that is located on the support side. The piezoelectric thin-film includes a region in which the IDT electrodes are provided and on which no support is provided but an opening is formed. This allows the IDT electrodes and the piezoelectric thin-film and the IDT electrode-formed region of the piezoelectric thin-film to not be in contact with the support, thereby defining a membrane including only the piezoelectric thin-film and the IDT electrodes as elements, the piezoelectric thin-film and the IDT electrodes being disposed therein and being important for properties of the piezoelectric device.

Abstract: A boundary acoustic wave device includes an IDT electrode between a piezoelectric layer and a dielectric layer. A low thermal expansion medium layer having a linear thermal expansion coefficient less than that of the piezoelectric layer is laminated on the piezoelectric layer opposite to the boundary. Acoustic velocities of transversal waves at the piezoelectric layer, the dielectric layer, and the low thermal expansion medium layer satisfy Expression (1), and (an acoustic velocity of a transverse wave at the dielectric layer)/? satisfies Expression (2) as follows: (acoustic velocity of transverse wave at dielectric layer)<(acoustic velocity of SH wave at piezoelectric layer)<(acoustic velocity of transverse wave at low thermal expansion medium layer)??Expression (1), and (response frequency of boundary acoustic wave)<(acoustic velocity of transverse wave at dielectric layer)/?<(response frequency of high order mode)??Expression (2).

Abstract: A method for producing a piezoelectric composite substrate with satisfactory productivity controls the inclination of the crystal axis and the polar axis of a single-crystal thin film and prevents an adverse effect due to pyroelectricity in a production process. The method for producing a piezoelectric composite substrate provided with a plurality of piezoelectric materials includes an ion-implantation step, a bonding step, and a separation step. In the ion-implantation step, H+ ions are implanted into a piezoelectric single crystal material. In the bonding step, the piezoelectric single crystal material is bonded to a piezoelectric single crystal material. At this time, the polarity of the polar surface of the piezoelectric single crystal material is opposite to the polarity of the polar surface of the piezoelectric single crystal material, the polar surfaces being bonded to each other.

Abstract: An elastic wave filter of a resonator type includes at least one IDT electrode arranged so as to contact the piezoelectric substance. The elastic wave filter is arranged such that an elastic wave in a main propagation mode for obtaining target frequency characteristics and an elastic wave in a sub-propagation mode propagate, the elastic wave being capable of propagating simultaneously with the elastic wave in the main propagation mode, an electromechanical coefficient K2 of the elastic wave in the sub-propagation mode is in the range from about 0.1% to about one third of an electromechanical coefficient K2 of the elastic wave in the main propagation mode, and a sound velocity of the elastic wave in the sub-propagation mode differs from a sound velocity of the elastic wave in the main propagation mode.

Abstract: A boundary acoustic wave device includes a first medium, a second medium, a third medium, and a fourth medium that are laminated in that order and, an electrode including an IDT electrode disposed at an interface between the first medium and the second medium, the temperature coefficient of delay time TCD of a boundary acoustic wave has a positive value, the fourth medium or the second medium has a positive temperature coefficient of sound velocity TCV, the first medium has a negative temperature coefficient of sound velocity TCV, and the sound velocity of transverse wave of the third medium is set to be less than the sound velocity of transverse wave of the fourth medium and/or the second medium.

Abstract: In a method for manufacturing a piezoelectric device, an ion implantation layer is formed at a desired depth from one principal surface of a piezoelectric single crystal substrate by implanting hydrogen ions into the piezoelectric single crystal substrate under desired conditions. The piezoelectric single crystal substrate in which the ion implantation layer has been formed is bonded to a supporting substrate, and THG laser light is irradiated from the supporting substrate side. Since the optical absorptance of the piezoelectric single crystal substrate to the THG laser light is higher than that of the supporting substrate, the irradiated light is absorbed primarily at the bonding surface side of the piezoelectric single crystal with the supporting substrate and heat is locally generated.

Abstract: A boundary acoustic wave device includes a solid layer laminated onto a single crystal substrate, electrodes provided between the single crystal substrate and the solid layer, and boundary acoustic wave elements provided on the single crystal substrate having the same cut angle, wherein the propagation direction of one of the boundary acoustic wave elements is different from that of at least one of the other boundary acoustic wave elements. A compact and high-performance boundary acoustic wave device using a boundary acoustic wave is provided by increasing the steepness of a filter band and by forming filters or resonators with different fractional bandwidths on a single substrate.

Abstract: A lower electrode and an adhesive layer made of an insulator are formed on a back surface on the ion implantation layer side of a piezoelectric single crystal substrate. A supporting substrate in which sacrificial layers made of a conductive material have been formed is bonded to the surface of the adhesive layer. By heating the composite body including the piezoelectric single crystal substrate, the lower electrode, the adhesive layer, and the supporting substrate, a layer of the piezoelectric single crystal substrate is detached to form a piezoelectric thin film. A liquid polarizing upper electrode is formed on a detaching interface of the piezoelectric thin film. A pulsed electric field is applied using the polarizing upper electrode and the sacrificial layers as counter electrodes. Consequently, the piezoelectric thin film is polarized.

Abstract: A method for producing a piezoelectric composite substrate having a single-crystal thin film of a piezoelectric material includes an ion-implantation step and a separation step. In the ion-implantation step, He+ ions are implanted into the single-crystal base made of the piezoelectric material to form localized microcavities in a separation layer located inside the single-crystal base and apart from a surface of the single-crystal base. In the separation step, the microcavities formed in the ion-implantation step are subjected to thermal stress to divide the separation layer of the piezoelectric single-crystal base, thereby detaching the single-crystal thin film.

Abstract: A method for manufacturing a composite piezoelectric substrate is capable of forming an ultra-thin piezoelectric film having a uniform thickness by efficiently using a piezoelectric material.

Abstract: A boundary acoustic wave device includes a stacked structure including a second medium, an IDT electrode, and a first medium, the stacked structure including the first medium having a temperature coefficient of group delay time TCD that is positive. The IDT electrode is stacked on the first medium. The second medium is stacked on the first medium so as to cover the IDT electrode and has a temperature coefficient of group delay time TCD that is negative. A third medium having an acoustic velocity of a transverse wave that is less than an acoustic velocity of a transverse wave of the second medium is arranged at least on a top surface of the IDT electrode.

Abstract: An acoustic wave element includes an IDT electrode in contact with a piezoelectric material and including a plurality of electrode fingers, which include first and second electrode fingers that adjoin each other in an acoustic wave propagation direction and that connect to different potentials and a first dummy electrode finger facing the first electrode finger via a gap located on an outer side in an electrode finger length direction of the first electrode finger. At an area near the gap, first protrusions are provided in at least one of the first electrode finger and the first dummy electrode finger, the first protrusion protruding in the acoustic wave propagation direction from at least one of side edges of the at least one of the first electrode finger and the first dummy electrode finger. The acoustic wave element has greatly improved resonance characteristics of a resonance frequency and prevents short-circuit failure between electrode fingers and degradation in insulation properties.

Abstract: A boundary acoustic wave filter device capable of increasing an out-of-band attenuation includes a dielectric film formed on a piezoelectric substrate, at least one longitudinally coupled resonator boundary acoustic wave filter having a plurality of IDTs disposed along a boundary between the piezoelectric substrate and the dielectric film, and at least two one-terminal-pair boundary acoustic wave resonators. At least one boundary acoustic wave resonator is connected in series to the longitudinally coupled resonator boundary acoustic wave filter, and at least remaining one boundary acoustic wave resonator is connected in parallel to the longitudinally coupled resonator boundary acoustic wave filter.

Abstract: A method for manufacturing a boundary acoustic wave device prevents formation of discontinuous portions in a dielectric film without a significant decrease in the thickness of an IDT when the dielectric film is formed by deposition and without deterioration of electrical characteristics. The method includes the steps of forming an IDT on a piezoelectric substrate, forming a lower dielectric film so as to cover the IDT, conducting a planarizing step so as to smooth the rough surface of the lower dielectric film, and forming an upper dielectric film so as to cover the lower dielectric film of which the rough surface is smoothed.

Abstract: A boundary acoustic wave device includes an IDT electrode between a piezoelectric layer and a dielectric layer. A low thermal expansion medium layer made of a material having a linear thermal expansion coefficient less than that of the piezoelectric layer is laminated on a surface of the piezoelectric layer opposite to the boundary.

Abstract: In a method for producing a boundary acoustic wave device that includes a first medium, a second medium, and a third medium laminated in that order, and electrodes disposed at the interface between the first medium and the second medium, the method includes the steps of preparing a laminate including the first medium, the second medium, and the electrodes disposed at the interface between the first medium and the second medium, adjusting the thickness of the second medium after the step of preparing the laminate to regulate a frequency or the acoustic velocity of a surface acoustic wave, a pseudo-boundary acoustic wave, or a boundary acoustic wave, after the adjusting step, forming the third medium different from the second medium in terms of the acoustic velocity with which the boundary acoustic wave propagates therethrough and/or in terms of material.

Abstract: A method for manufacturing a boundary acoustic wave device includes the steps of preparing a laminated structure in which an IDT electrode is disposed at an interface between first and second solid media and reforming the first medium and/or the second medium by externally providing the laminated structure with energy capable of reaching the inside of the first medium and/or the second medium and thus adjusting a frequency of the boundary acoustic wave device. The above provides a boundary acoustic wave device manufacturing method that enables frequency adjustment to be readily performed with high accuracy.

Abstract: A boundary acoustic wave device includes an IDT electrode disposed at the boundary between a first medium and a second medium, the IDT electrode having electrode fingers, in which a third medium is arranged between the electrode fingers of the IDT electrode, the third medium having an acoustic impedance ZB3 satisfying Expression (1), wherein ZB2 is the acoustic impedance of the second medium and ZIDT is the acoustic impedance of the IDT electrode: |ZB3/ZIDT?1|<|ZB2/ZIDT?1|??Expression (1).

Abstract: A boundary acoustic wave device includes a first medium, a second medium, and an IDT electrode disposed at an interface between the first medium and the second medium, the IDT electrode having an Au layer defining a main electrode layer, wherein a Ni layer is laminated so as to contact at least one surface of the Au layer, and a portion of Ni defining the Ni layer is diffused from the Ni layer side surface of the Au layer toward the inside of the Au layer.