Elements, electronic devices, electronic equipment and systems

Abstract

[Problem] To provide a surface acoustic wave element that is environmentally friendly and has superior accuracy, and an electronic device, an electronic apparatus, and a system in which the surface acoustic wave element is used. [Solution] In an element that includes a circular or substantially circular piezoelectric body and one or more interdigital electrodes provided on the piezoelectric body so that a surface acoustic wave can propagate in the circumferential direction or a substantially circumferential direction, the piezoelectric body in the propagation path of the surface acoustic wave is fitted with a reflector, to thereby fabricate a high-accuracy sensor that uses a bulk acoustic wave generated between the surface acoustic wave and piezoelectric body and the reflector.

Description

[Technical field]

[0001] The present invention relates to an element, an electronic device, an electronic instrument, and a system that use a piezoelectric material. [Background technology]

[0002] A surface acoustic wave (SAW) element, which is a type of piezoelectric element, has an interdigital transducer (IDT) on a piezoelectric substrate such as a quartz substrate. The interdigital transducer is formed in pairs on the piezoelectric substrate so that the comb-shaped electrodes face each other without contact. By applying an AC voltage to the interdigital transducer, the piezoelectric effect and inverse piezoelectric effect of the piezoelectric substrate can vibrate the surface or near the surface of the piezoelectric substrate on which the interdigital transducer is formed in a frequency band. Depending on the combination and configuration of the interdigital transducers, surface acoustic wave elements are widely used in electronic circuits that make up various electronic devices such as oscillators, bandpass filters, and gyros.

[0003] In recent years, for example, as mobile terminal devices used in mobile communications become smaller and lighter, there is a demand for acoustic wave elements with higher accuracy to achieve high communication quality, and in order to meet such demands, spherical SAW sensors (ball SAW sensors) and the like have been considered (Patent Document 1). Ball SAW sensors are useful for increasing sensitivity because they can increase the interaction distance significantly compared to planar sensors by utilizing the phenomenon in which a natural collimated beam of SAW makes multiple rounds. However, when used in gas sensors, for example, the sensitive film used in the gas sensor increases the attenuation of SAW, preventing high sensitivity. In addition, SAW devices have many issues with high frequency characteristics and correction methods for high sensitivity, and are still not satisfactory. Furthermore, with the demand for energy saving for environmental issues, etc., a new SAW element that can solve these issues has been awaited. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-115084 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a surface acoustic wave element that is environmentally friendly and has excellent precision, as well as an electronic device, electronic equipment, and system that use the surface acoustic wave element. [Means for solving the problem]

[0006] As a result of intensive research into achieving the above-mentioned object, the inventors have discovered that, in an element including a circular or approximately circular piezoelectric body, in which one or more interdigital transducers are provided on the piezoelectric body so that surface acoustic waves can propagate in a circumferential or approximately circumferential direction, by providing a reflector on the piezoelectric body within the propagation path of the surface acoustic waves, it is surprisingly possible to easily utilize correction due to phase difference using the Sagnac effect, and further, by using a reflector, it is possible to succeed in achieving high sensitivity and saving energy, and have found that such an element can solve the above-mentioned conventional problems in one fell swoop. After obtaining the above findings, the present inventors conducted further studies and completed the present invention.

[0007] That is, the present invention relates to the following inventions. [1] An element including a circular or nearly circular piezoelectric body, in which one or more interdigital transducers are provided on the piezoelectric body so that surface acoustic waves can propagate in a circumferential or nearly circumferential direction, and characterized in that a reflector is provided on the piezoelectric body within the propagation path of the surface acoustic waves. [2] The element according to [1], wherein the piezoelectric body is cylindrical, approximately cylindrical, barrel-shaped or approximately barrel-shaped. [3] The element according to [1] or [2], wherein two or more of the interdigital transducers are provided on either side of the reflector. [4] The element according to any one of [1] to [3], wherein the interdigital transducer comprises a SAW generating means for generating the surface acoustic wave and a SAW receiving means for receiving the surface acoustic wave. [5] The element according to any one of [1] to [4], wherein an electrode for detecting a signal resulting from a surface acoustic wave propagating from the interdigital transducer is provided on a surface of the piezoelectric body that is parallel to the circumferential direction or the approximately circumferential direction. [6] The element according to [5], wherein the signal is an SH wave propagating in a direction perpendicular to the propagation direction of the surface acoustic wave. [7] The element according to any one of [1] to [6], wherein the piezoelectric body is a single crystal made of a piezoelectric material having a trigonal or hexagonal crystal structure. [8] The element according to [7], wherein the surface acoustic wave is configured to propagate on the c-plane of the single crystal. [9] The element according to [7] or [8], further comprising an electrode on the a-plane or m-plane of the single crystal for reading bulk acoustic waves propagating on the a-plane or m-plane.

[10] The element according to any one of [1] to [9], wherein the piezoelectric body is layered on a crystal substrate via a buffer layer by epitaxial crystal growth.

[11] The element according to

[10] above, wherein the buffer layer comprises a metal oxide containing Hf or Zr.

[12] An electronic device including a piezoelectric element, wherein the piezoelectric element is an element according to any one of [1] to

[11] above.

[13] The electronic device according to

[12] , which is a sensor.

[14] An electronic device including an electronic device, the electronic device being the electronic device described in

[12] or

[13] .

[15] A system including an electronic device, characterized in that the electronic device is the electronic device described in

[14] . Effect of the Invention

[0008] The element of the present invention is a surface acoustic wave element that is environmentally friendly and has excellent precision, and the electronic device, electronic equipment, and system of the present invention are equipped with the surface acoustic wave element and are environmentally friendly and can exhibit the high-precision characteristics of the surface acoustic wave element. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of an example of a preferred embodiment of the element of the present invention. [Diagram 2] FIG. 2 is a diagram illustrating an example of a reflector that can be suitably used in the element of the present invention. [Diagram 3] FIG. 2 is a diagram illustrating an example of another preferred embodiment of the element of the present invention. [Figure 4] 1A to 1C are diagrams for explaining the propagation direction and the perpendicular direction of the surface acoustic wave in the element of the present invention, and correction and the like using these. [Diagram 5] FIG. 2 is a schematic diagram showing a film forming apparatus preferably used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The element of the present invention includes a circular or approximately circular piezoelectric body, and one or more interdigital transducers are provided on the piezoelectric body so that surface acoustic waves can propagate in a circumferential or approximately circumferential direction. The element is characterized in that a reflector is provided on the piezoelectric body within the propagation path of the surface acoustic waves.

[0011] The reflector is not particularly limited as long as it is provided on the piezoelectric body within the propagation path of the surface acoustic wave (hereinafter also referred to as "SAW"), and may be a known reflector, but in the present invention, it is preferable that the reflector is located adjacent to an interdigital transducer (hereinafter also referred to as "IDT electrode") in the propagation direction of the SAW, for example, as shown in Fig. 1. The reflector may be, for example, an electrode formed in a lattice shape, and in the present invention, it is preferable that the reflector has a pair of mutually opposing reflection bus bars 21 and a plurality of reflection electrode fingers 23 extending between the pair of reflection bus bars 21, as shown in Fig. 2.

[0012] The shape and dimensions of the reflective busbar 21 and the reflective electrode fingers 23 in FIG. 2 may be basically the same as those of the busbar and electrode fingers of the IDT electrode, except that both ends of each reflective electrode finger 23 are connected to a pair of reflective busbars 21. For example, each reflective electrode finger 23 has an elongated shape that extends linearly in a direction (direction D2) perpendicular to the propagation direction of the SAW with a certain width, and has the same length as each other. For example, the multiple reflective electrode fingers 23 are arranged side by side in the propagation direction of the SAW. The number of the multiple reflective electrode fingers 23 is usually set so that the reflectance of the SAW in the mode intended to be used is approximately 100% or more. A theoretically necessary minimum number is, for example, several to about 10, and the number of the reflective electrode fingers 23 is preferably 20 or more.

[0013] The reflector is usually not electrically connected to the IDT electrode, and may be in an electrically floating state (a state in which no potential is applied from the outside), or may be applied with a reference potential, etc. In the present invention, the reflector may be electrically connected to one electrode portion of the IDT electrode, but is preferably in an electrically floating state (a state in which no potential is applied from the outside).

[0014] In the present invention, it is preferable that the element includes a SAW generating means for generating the surface acoustic wave and a SAW receiving means for receiving the surface acoustic wave, and it is also preferable that an electrode for detecting a signal caused by the surface acoustic wave propagated from the interdigital transducer is provided on a surface parallel to the circumferential direction or the approximately circumferential direction of the piezoelectric body. The signal is not particularly limited as long as it is a signal caused by the surface acoustic wave, and is usually a signal propagating in a direction perpendicular to the propagation direction of the surface acoustic wave, but in the present invention, it is preferable that it is an SH wave propagating in a direction perpendicular to the propagation direction of the surface acoustic wave. According to such a preferable range, it is possible to more easily improve the accuracy of correction using the signal, and a more sensitive sensor can be realized. In the present invention, it is more preferable that the interdigital transducer is provided on two or more sides of the reflector, for example as shown in FIG. 3, and by configuring in this way, it is possible to further improve the accuracy of correction using the signal, and a more sensitive sensor can be more easily realized.

[0015] Here, a preferred example of the correction using the signal is shown. As shown in Fig. 4, when a voltage is applied to interdigital transducers 13a and 13b, the voltage is applied to piezoelectric body 3 by the electrode fingers of the interdigital transducer, and a SAW of a predetermined mode is excited, which propagates along piezoelectric body 3 in the directions D1 and D2. The excited SAW is mechanically reflected by the electrode fingers of interdigital transducers 13a and 13b and reflector 9, and a standing wave is formed with the pitch of the electrode fingers as a half wavelength. The standing wave is converted into an electric signal of the same frequency as the standing wave, and is extracted by the electrode fingers of the interdigital transducer. Here, a phase difference occurs between the wave in the D1 direction and the wave in the D2 direction propagating in the SAW to which the rotational angular velocity has been applied, and therefore correction, for example, using the following formula (1) that expresses the phase difference is possible.

number

[0016] In addition, the reflector 9 strengthens the standing wave in the IDT electrodes 13a, 13b, improving the function as a resonator. Furthermore, for example, at the boundary between the IDT electrodes 13a, 13b and the reflector 9, part of the SAW is converted into a bulk wave and enters the piezoelectric body 3, making it possible to preferably extract a signal propagating in a direction perpendicular to the propagation direction of the surface acoustic wave, i.e., in the D3 direction, and making it possible to perform corrections, etc. using these signals.

[0017] The piezoelectric body is not particularly limited as long as it includes a circular or approximately circular piezoelectric body, and may have any shape, but in the present invention, the piezoelectric body is preferably cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped. These suitable shapes can also be obtained by processing according to a conventional method. The material of the piezoelectric body is also not particularly limited as long as it is made of a piezoelectric material, but in the present invention, it is preferable that it is a piezoelectric material having a trigonal or hexagonal crystal structure. In addition, in the present invention, it is preferable that the piezoelectric body is a single crystal, and more preferably a single crystal made of a piezoelectric material having a trigonal or hexagonal crystal structure. According to such a preferable range, it is possible to achieve higher sensitivity and to make the element more environmentally friendly. In addition, when the piezoelectric body is a single crystal made of a piezoelectric material having a trigonal or hexagonal crystal structure, it is preferable that the element is configured so that the surface acoustic wave propagates on the c-plane of the single crystal, and it is also preferable that an electrode for reading a bulk acoustic wave propagating on the a-plane or m-plane of the single crystal is provided on the a-plane or m-plane. Within such a preferable range, it is possible to easily achieve a further increase in sensitivity of the element.

[0018] In the present invention, the piezoelectric body is preferably laminated on a crystal substrate via a buffer layer by epitaxial crystal growth. The buffer layer is not particularly limited as long as it does not impede the object of the present invention, but preferably contains a metal compound containing Hf or Zr, and preferably contains a metal oxide containing Hf or Zr. The metal compound is not particularly limited as long as it does not impede the object of the present invention, and may be a known metal compound. It may be an oxide or a nitride. In the present invention, the metal oxide is usually a crystalline metal oxide, but it is also preferable that the crystalline metal oxide contains 50 atomic % or more of Hf and / or Zr and 0.1 atomic % to 50 atomic % of one or more metals selected from Al, Ti, Y and Ce among the constituent metals. According to such a preferable mixed crystal, not only the stress relaxation effect of the buffer layer is improved, but also the piezoelectric properties of the piezoelectric body can be improved.

[0019] The crystal substrate (hereinafter, simply referred to as "substrate") is not particularly limited as long as the object of the present invention is not hindered, such as the substrate material, and may be a known crystal substrate. It may be an organic compound or an inorganic compound. In the present invention, it is preferable that the crystal substrate contains an inorganic compound. In the present invention, it is preferable that the substrate has crystals on a part or all of the surface, more preferably a crystal substrate having crystals on all or a part of the main surface on the crystal growth side, and most preferably a crystal substrate having crystals on the entire main surface on the crystal growth side. The crystal is not particularly limited as long as the object of the present invention is not hindered, and the crystal structure is not particularly limited, but it is preferable that it is a cubic, tetragonal, trigonal, hexagonal, orthorhombic, or monoclinic crystal, and more preferably a trigonal or hexagonal crystal. In addition, the crystal substrate may have an off angle, and examples of the off angle include an off angle of 0.2° to 12.0°. Here, the "off angle" refers to the angle between the substrate surface and the crystal growth surface. The shape of the substrate is not particularly limited, but is not particularly limited as long as it is plate-shaped and serves as a support for the buffer layer. The substrate may be an insulating substrate or a semiconductor substrate, but in the present invention, the substrate is preferably a Si substrate, more preferably a crystalline Si substrate, and most preferably a crystalline Si substrate oriented in (100). In addition to the Si substrate, examples of the substrate material include one or more metals belonging to Groups 3 to 15 of the periodic table or oxides of these metals. The shape of the substrate is not particularly limited, and may be an approximately circular shape (e.g., a circular shape, an elliptical shape, etc.) or a polygonal shape (e.g., a triangular shape, a square shape, a rectangular shape, a pentagonal shape, a hexagonal shape, a heptagonal shape, an octagonal shape, a nonagonal shape, etc.), and various shapes can be suitably used. In addition, in the present invention, a large-area substrate can also be used.

[0020] In the present invention, the crystal substrate preferably has a flat surface, but it is also preferable that the crystal substrate has an uneven shape on a part or all of the surface, since this can improve the quality of the crystal growth of the epitaxial film. The crystal substrate having the uneven shape may have an uneven portion consisting of a concave or convex portion formed on a part or all of the surface, and the uneven portion is not particularly limited as long as it is composed of a convex portion or a concave portion, and may be an uneven portion consisting of a convex portion, an uneven portion consisting of a concave portion, or an uneven portion consisting of a convex portion and a concave portion. The uneven portion may be formed of regular convex portions or concave portions, or may be formed of irregular convex portions or concave portions. In the present invention, it is preferable that the uneven portion is formed periodically, and it is more preferable that the uneven portion is patterned periodically and regularly. The shape of the uneven portion is not particularly limited, and examples thereof include a stripe shape, a dot shape, a mesh shape, and a random shape, but in the present invention, a dot shape or a stripe shape is preferable, and a dot shape is more preferable. In addition, when the unevenness is patterned periodically and regularly, the pattern shape of the unevenness is preferably a polygonal shape such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon, a circle, or an ellipse. In addition, when the unevenness is formed in a dot shape, the lattice shape of the dots is preferably a lattice shape such as a square lattice, an oblique lattice, a triangular lattice, or a hexagonal lattice, and more preferably a triangular lattice shape. The cross-sectional shape of the concave or convex part of the unevenness is not particularly limited, but examples thereof include a U-shape, a U-shape, an inverted U-shape, a wave shape, or a polygonal shape such as a triangle, a quadrangle (for example, a square, a rectangle, or a trapezoid), a pentagon, or a hexagon. In addition, the thickness of the crystal substrate is not particularly limited, but is preferably 50 to 2000 μm, and more preferably 100 to 1000 μm.

[0021] Preferred embodiments of the present invention will now be described with reference to the drawings, but the present invention is not limited to these preferred embodiments.

[0022] FIG. 1 shows an example of a suitable element of the present invention. In the element of FIG. 1, a buffer layer 2 is formed on a crystal substrate 1 by epitaxial crystal growth, and a piezoelectric body 3 is formed on the buffer layer 2. The piezoelectric body 3 is processed into a cylindrical shape, and an interdigital transducer 13 and a reflector 9 are formed on the side. In addition, an extraction electrode 15 is formed on the upper surface of the piezoelectric body 3. The extraction electrode 15 is an electrode for detecting a signal caused by a surface acoustic wave propagating from the interdigital transducer, and is connected to a detector for detecting SH waves and the like propagating in a direction perpendicular to the propagation direction of the surface acoustic wave. The interdigital transducer 13, the reflector 9, and the extraction electrode may be formed by using known means. When a voltage is applied to the interdigital transducer 13, a strain is generated on the piezoelectric body between adjacent electrode fingers of the interdigital transducer 13 due to the piezoelectric effect of the piezoelectric body 3, and a surface wave is excited. The interdigital transducer has electrode fingers arranged periodically, and the surface wave is excited most strongly when the wavelength and the electrode finger period are equal. Since the frequency is determined by the distance between the electrodes formed on the surface, high frequencies can be easily accommodated by photolithography or other processing.

[0023] The element is suitably used in electronic devices according to the usual method. For example, the element can be connected as a piezoelectric element to a power source or an electric / electronic circuit, and mounted on a circuit board or packaged to form various electronic devices. In the present invention, the electronic device is preferably a piezoelectric device, and can be used as a piezoelectric device in electronic devices such as gyroscopes and motion sensors. In addition, for example, if an amplifier and a rectifier circuit are connected and packaged, the electronic device can be used as various sensors such as magnetic sensors.

[0024] The electronic device is suitably used in electronic devices in the usual manner, and can be applied to various electronic devices other than the above-mentioned electronic devices, and more specifically, suitable examples include liquid ejection heads, liquid ejection devices, vibration wave motors, optical devices, vibration devices, imaging devices, piezoelectric acoustic parts, audio playback devices having the piezoelectric acoustic parts, audio recording devices, mobile phones, various information terminals, and the like.

[0025] Furthermore, the electronic device is also applied to a system in the usual manner, and an example of such a system is a sensor system. EXAMPLES

[0026] (Example of Piezoelectric Body) The crystal growth surface side of the Si substrate (100) was treated by RIE, and then heated in the presence of oxygen to form a thermal oxide film. Then, without using oxygen, a metal from the deposition source was thermally reacted with oxygen in the oxide film on the Si substrate by a deposition method to form a single crystal of a crystalline metal oxide on the Si substrate. Next, oxygen was introduced, the temperature was lowered, and the pressure was increased, and a single crystal film of a crystalline metal oxide was formed as the crystal by a deposition method. The deposition conditions during this film formation were as follows: Vapor deposition source: Hf, Zr Voltage: 3.5~4.75V Pressure: 3×10 -2 ~6×10 -2 Pa Substrate temperature: 450~700℃

[0027] The deposition apparatus used for forming a single crystal film of a crystalline metal oxide is shown in Fig. 5. The deposition apparatus in Fig. 5 includes at least a crucible, metal sources 1101a-1101b, earths 1102a-1102h, ICP electrodes 1103a-1103b, cut filters 1104a-1104b, DC power sources 1105a-1105b, RF power sources 1106a-1106b, lamps 1107a-1107b, Ar source 1108, reactive gas source 1109, power source 1110, substrate holder 1111, substrate 1112, cut filter 1113, ICP ring 1114, vacuum chamber 1115, and rotation shaft 1116. The ICP electrodes 1103a-1103b in Fig. 13 have a substantially concave curved shape or a parabolic shape curved toward the center of the substrate 1112.

[0028] As shown in FIG. 5, the substrate 1112 is fixed on the substrate holder 1111. Then, the rotating shaft 1116 is rotated using the power supply 1110 and a rotating mechanism (not shown) to rotate the substrate 1112. The substrate 112 is heated by the lamps 1107a-1107b, and the inside of the vacuum chamber 1115 is evacuated to a vacuum or reduced pressure by a vacuum pump (not shown). Then, Ar gas is introduced from the Ar source 1108 into the vacuum chamber 1115, and argon plasma is formed on the substrate 1112 using the DC power supplies 1105a-1105b, the RF power supplies 1106a-1106b, the ICP electrodes 1103a-1103b, the cut filters 1104a-1104b, and the earths 1102a-1102h, thereby cleaning the surface of the substrate 1112.

[0029] Ar gas is introduced into the vacuum chamber 1115, and a reactive gas is introduced using a reactive gas source 1109. At this time, lamps 1107a to 1107b, which are lamp heaters, are alternately turned on and off repeatedly, so that a crystal growth film of better quality can be formed.

[0030] Next, a platinum (Pt) metal film was formed as a conductive film on the single crystal film of the crystalline metal oxide by sputtering under the following conditions. Equipment: ULVAC sputtering equipment QAM-4 Pressure: 1.20×10 -1 Pa Target: Pt Power: 100W(DC) Thickness: 100nm Substrate temperature: 450~600℃

[0031] Next, an SRO film was formed on the conductive film by sputtering under the following conditions. Equipment: ULVAC sputtering equipment QAM-4 Power: 150W(RF) Gas: Ar Pressure: 1.8Pa Substrate temperature: 600℃ Thickness: 20nm

[0032] Next, a Pb(Zr 0.52 Ti 0.48 The conditions for this are as follows:

[0033] Lead acetate was used as the raw material for Pb, zirconium nitrate was used as the raw material for Zr, and titanium isopropoxide was used as the raw material for Ti. The raw materials for Pb, Zr, and Ti were mixed to a composition ratio of Pb:Zr:Ti=100+δ:52:48, and the solvent was pure water in consideration of the solubility of the raw materials, with acetic acid added to control hydrolysis. Furthermore, ethanol (0.5-3.0 mol per 1 mol of PZT) in which polyvinylpyrrolidone powder had been mixed and dissolved was added to adjust the viscosity. Finally, an appropriate amount of 2n-butoxyethanol was mixed to adjust the wettability during application, and a sol-gel solution was prepared as the raw material solution.

[0034] Next, the prepared sol-gel solution was dropped onto a substrate and rotated at 2000 rpm for 1 minute to spin coat (apply) the sol-gel solution onto the substrate to form a film containing the precursor. The substrate was then placed on a hot plate at 150°C, and then placed on a hot plate at 350°C to evaporate the solvent and dry the film. This process was repeated five times to stack five layers under the same conditions, and then the precursor was oxidized and crystallized by heat treatment at 650°C for 3 minutes in an oxygen (O2) atmosphere. The above process was repeated 10 times to obtain Pb(Zr 0.52 Ti 0.48 The total thickness of the film was 10 μm.

[0035] Examples of application of the obtained piezoelectric material to elements will be described in more detail below with reference to the drawings, but the present invention is not limited to these examples. In the present invention, unless otherwise specified, elements, electronic devices, etc. can be manufactured from the piezoelectric material by known means.

[0036] FIG. 3 shows an example of an element according to a preferred embodiment of the present invention. The element in FIG. 3 differs from that in FIG. 1 in that two interdigital transducers are provided on either side of the reflector. The element in FIG. 3 also includes an SH wave detector for detecting the SH wave and a SAW receiver for detecting the SAW. In the element in FIG. 3, a piezoelectric body 3 is processed into a cylindrical shape, and interdigital transducers 13a, 13b and a reflector 9 are formed on the side surface of the piezoelectric body 3 by known means. An extraction electrode 15 is formed on the upper surface of the piezoelectric body 3 by a conventional method. The extraction electrode 15 is connected to an SH wave detector 18 that detects SH waves propagating in a direction perpendicular to the propagation direction of the surface acoustic wave. The interdigital transducers 13a, 13b, the reflector 9, and the extraction electrode may each be formed by known means. When a voltage is applied to the interdigital transducers 13a and 13b, the piezoelectric effect of the piezoelectric body 3 generates strain on the piezoelectric body between the adjacent electrode fingers of the interdigital transducers 13a and 13b, exciting a surface wave. A SAW receiver 19 is connected to the interdigital transducer 13a, and is configured to detect the surface acoustic wave propagating in the SAW propagation path. The surface acoustic wave propagates in the directions D1 and D2 shown in Fig. 4 on the surface of the piezoelectric body 3 by the reflector 9, that is, the surface acoustic waves propagate in the directions opposite to each other, which generates a phase difference. The bulk acoustic wave generated between the interdigital transducers 13a and 13b and the reflector 9 is detected via the extraction electrode 15, and an environmentally friendly sensor that uses the surface acoustic wave and the bulk acoustic wave can be fabricated with high accuracy and sensitivity. [Industrial Applicability]

[0037] The element of the present invention can be used for various purposes, but is particularly suitable for use as a piezoelectric sensor, and is applied to, for example, electronic devices for sensor systems. [Explanation of symbols]

[0038] 1. Crystal Substrate 2. Buffer layer 3. Piezoelectric 9 reflector 10 elements 13 Interdigital Electrode 13a Interdigital electrode 13b Interdigital electrode 15 Extraction electrode 18 SH wave detector 19 SAW Receiver 21 Reflective busbar 23 Reflector electrode finger 1101a~101b Metal source 1102a~102j Earth 1103a~103b ICP electrode 1104a~104b Cut Filter 1105a~105b DC power supply 1106a~106b RF power supply 1107a~107b Lamp 1108 Ar source 1109 Reactive Gas Source 1110 Power supply 1111 PCB holder 1112 Substrate 1113 Cut Filter 1114 ICP Ring 1115 Vacuum chamber 1116 Rotating shaft

Claims

1. An element including a cylindrical, approximately cylindrical, barrel-shaped, or approximately barrel-shaped piezoelectric body, one or more interdigital transducers provided on a side surface of the piezoelectric body so that a surface acoustic wave can propagate in a circumferential direction, and a reflector provided on the side surface that is within a propagation path of the surface acoustic wave, the piezoelectric body is a single crystal made of a piezoelectric material having a trigonal or hexagonal crystal structure, The element further comprises a first electrode for reading bulk acoustic waves propagating on the a-plane or m-plane of the single crystal, the first electrode being provided on the a-plane or m-plane, which is the upper surface of the piezoelectric body.

2. 2. The element according to claim 1, wherein two or more of said interdigital transducers are provided on either side of said reflector.

3. 2. The element of claim 1, wherein said inter-digital transducer comprises SAW generating means for generating said surface acoustic waves and SAW receiving means for receiving said surface acoustic waves.

4. 2. The element of claim 1, wherein the surface acoustic wave is configured to propagate on a c-plane of the single crystal.

5. 2. The element according to claim 1, wherein the piezoelectric body is layered on a crystal substrate via a buffer layer by epitaxial crystal growth.

6. The device of claim 5 , wherein the buffer layer comprises a metal oxide comprising Hf or Zr.

7. 13. An electronic device including a piezoelectric element, the piezoelectric element being the element according to claim 1.

8. The electronic device of claim 7 which is a sensor.

9. 8. An electronic device including an electronic device, the electronic device being the electronic device according to claim 7.

10. A system including an electronic device, the electronic device being the electronic device according to claim 9.

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