Device for elastic shafts

Abstract

Device for elastic waves (1) comprising a piezoelectric film, comprising: a material with a high speed of sound (7) in which the speed of sound of a volume wave propagating through the material with the high speed of sound is higher than that of an elastic wave propagating through the piezoelectric film, and a low-speed sound film (8) laminated onto the high-speed sound material and in which the speed of sound of a volume wave propagating through the low-speed sound film is lower than that of the elastic wave propagating through the piezoelectric film, wherein the piezoelectric film (9) is laminated onto the low sound velocity film and wherein an IDT electrode (3) is formed on a top side of the piezoelectric film opposite the low-speed sound film (8), wherein the IDT electrode (3) comprises: a first busbar (11), a second busbar (12) arranged separately from the first busbar, several first electrode fingers (13) whose proximal ends are electrically connected to the first busbar (11) and whose distal ends extend towards the second busbar (12), and several second electrode fingers (14) whose proximal ends are connected to the second busbar (12) and whose distal ends extend towards the first busbar (11), wherein, if a direction orthogonal to a direction in which the first electrode fingers (13) and the second electrode fingers (14) extend is defined as a width direction, the first electrode fingers (13) or the second electrode fingers (14) or the first electrode fingers and the second electrode fingers (13, 14) are provided with electrode fingers containing a wide section (13a-d, 14a-d), wherein the wide sections have a dimension in the width direction that is greater than a dimension of the electrode fingers at their midpoint in the longitudinal direction, wherein the wide sections (13a-d, 14a-d) are arranged in an overlap region of the electrode fingers (13, 14) closer to at least one of the proximal end and the distal end than a middle region (V1), wherein at least one of the first busbar (11) and the second busbar (12) has several cavities (15) distributed in a longitudinal direction of the first busbar (11) or the second busbar (12), and wherein the first busbar (11) and the second busbar (12) each contain an inner busbar section (11A) which is positioned closer to one side of the first electrode fingers (13) or one side of the second electrode fingers (14) than the cavities (15) and which extends in the longitudinal direction of the first busbar (11) and the second busbar (12), a middle busbar section (11B) which has the cavities (15), and an outer busbar section (11C) which is positioned opposite the inner busbar section (11A), while the middle busbar section (11B) is arranged in between.

Description

TECHNICAL AREA

[0001] The present invention relates to a device for elastic waves, which is used, for example, in a resonator or a bandpass filter. STATE OF THE ART

[0002] To this day, elastic wave devices are widely used as resonators or bandpass filters. JP 2011-101350 A and WO 2011 / 088904 A1 disclose a surface sound wave device structure that prevents a transient component in transverse modes by providing a piston mode. For example, electrode fingers of an IDT electrode in Fig. 9 in JP 2011-101350 A and in Fig. 4 in WO 2011 / 088904 A1 below, sections with large widths. By providing the sections with large widths, a region with low sound velocity is created.

[0003] According to Fig. 12 of JP 2011-101350 A and according to the Fig. 8 (c) and Fig. According to WO 2011 / 088904 A1, a film is laminated onto a portion of the IDT electrode. More precisely, the film is laminated in a region extending outwards from a central region, in the direction of the IDT electrode fingers. This forms a low-speed region.

[0004] An electroacoustic transducer according to US 2013 / 0051588 A1 comprises a central excitation area, inner boundary areas flanking the central excitation area, outer boundary areas flanking the inner boundary areas, and areas flanking the outer boundary areas of a busbar, resulting in the excitation profile of a piston mode. SUMMARY OF THE INVENTION Technical Problem

[0005] In a structure where the electrode fingers contain a wide section, there is a limit to how wide these sections can be. If the width is too large, the wide sections will touch adjacent electrode fingers. Consequently, the sound velocity in the low-speed region cannot be sufficiently reduced. Therefore, it is difficult to reliably suppress transverse modes. Furthermore, laminating an additional layer involves complex steps and is expensive.

[0006] It is an object of the present invention to provide a device for elastic shafts that can suppress transverse mode waviness without complicating the manufacturing steps and increasing the costs. Solution to the problem

[0007] According to the present invention, an elastic wave device is provided, comprising a piezoelectric film and a high-speed sound material in which the speed of sound of a volume wave propagating through the high-speed sound material is higher than that of an elastic wave propagating through the piezoelectric film, and a low-speed sound film laminated onto the high-speed sound material in which the speed of sound of a volume wave propagating through the low-speed sound film is lower than that of the elastic wave propagating through the piezoelectric film, wherein the piezoelectric film is laminated onto the low-speed sound film and an IDT electrode is formed on a surface of the piezoelectric film.The IDT electrode contains a first busbar, a second busbar which is arranged separately from the first busbar, several first electrode fingers whose proximal ends are electrically connected to the first busbar and whose distal ends extend towards the second busbar, and several second electrode fingers whose proximal ends are connected to the second busbar and whose distal ends extend towards the first busbar.If a direction orthogonal to a direction in which the first and second electrode fingers extend is defined as a lateral direction, then the first or second electrode fingers, or both the first and second electrode fingers, are provided with electrode fingers that have a wide section, wherein the wide sections have a dimension in the lateral direction that is greater than a dimension of the electrode fingers at their center in the longitudinal direction, and wherein the wide sections are provided in an overlap region of the electrode fingers closer to at least one of the proximal and distal ends than to a central region. At least one of the first busbars and the second busbar has multiple cavities distributed in a longitudinal direction of the first busbar or the second busbar.The first busbar and the second busbar contain an inner busbar section that is positioned closer to one side of the first electrode fingers or one side of the second electrode fingers than the cavities and that extends in the longitudinal direction of the first busbar and the second busbar, a middle busbar section that has the cavities, and an outer busbar section that is positioned opposite the inner busbar section, while the middle busbar section is arranged in between.

[0008] In a specific embodiment of the device for elastic waves according to the present invention, each inner busbar section has the form of a band that extends in a propagation direction of elastic waves.

[0009] In another specific embodiment of the device for elastic waves according to the present invention, the first electrode fingers and the second electrode fingers each contain the wide section. In this case, it is possible to suppress waviness even more effectively.

[0010] In a further specific embodiment of the device for elastic waves according to the present invention, the first electrode fingers or the second electrode fingers, or the first and second electrode fingers, each contain several of the wide sections. In this case, it is possible to suppress waviness even more effectively.

[0011] In another specific embodiment of the device for elastic shafts according to the present invention, the IDT electrode is a normal IDT electrode that is not subjected to apodization weighting. In this case, it is possible to form the IDT electrode in a simple manner.

[0012] In a further specific embodiment of the elastic wave device according to the present invention, when a wavelength of a surface sound wave is λ, the distance between the distal end of each first electrode finger and the second busbar relative to the distal end of each first electrode finger, and the distance between the distal end of each second electrode finger and the first busbar relative to the distal end of each second electrode finger, are 0.5 λ or less. In this case, the width of a high-speed sound section in a low-speed sound region can be designed to be small. Therefore, a propagation mode can be brought closer to an ideal piston mode.

[0013] In a further specific embodiment of the device for elastic waves according to the present invention, the device for elastic waves further comprises a support substrate that supports the high-speed sound material, and the high-speed sound material is a high-speed sound film.

[0014] In another specific embodiment of the device for elastic waves according to the present invention, the high-speed sound material is a high-speed sound support substrate.

[0015] In a further specific embodiment of the elastic wave device according to the present invention, the polarity of at least one electrode finger in the IDT electrode is reversed, and an electrode material is embedded in a gap between the electrode finger whose polarity has been reversed and adjacent electrode fingers on both sides. That is, if the elastic wave device is a filter, it is possible to increase the steepness of the filter characteristic.

[0016] In a further specific embodiment of the device for elastic shafts according to the present invention, the IDT electrode consists of Al or an alloy whose main component is Al, and the electrode film thickness of the IDT electrode is 0.08 λ or more. In this case, the resistance of the electrode fingers can be designed to be low.

[0017] In a further specific embodiment of the device for elastic waves according to the present invention, the film thickness of the IDT electrode is 0.10 λ or more and 400 nm or less. In this case, the resistance of the electrode fingers can be designed to be low.

[0018] In another specific embodiment of the elastic wave device according to the present invention, the high-speed sound material is a silicon substrate, and its specific volume resistivity is 1000 Ωcm or more. This means that if the elastic wave device is a filter, it is possible to reduce the filter's insertion loss.

[0019] In another specific embodiment of the elastic wave device according to the present invention, the high-speed sound material is a silicon substrate, and its specific volume resistivity is 4000 Ωcm or more. This means that if the elastic wave device is a filter, it is possible to increase the steepness of the filter characteristic. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0020] With the elastic shaft device of the present invention, it is possible to provide a piston mode and effectively suppress transverse mode waviness. Furthermore, it is not necessarily required to laminate an additional film to provide the piston mode. Therefore, it is unlikely that manufacturing steps will become more complicated or costs will increase. Moreover, it is possible to improve the quality. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a partially opened plan view of a main section of a device for elastic shafts according to a first embodiment of the present invention. Fig. Figure 2 is a schematic front sectional view of the device for elastic shafts according to the first embodiment of the present invention. Fig. Figure 3 is a schematic plan view of the device for elastic shafts according to the first embodiment of the present invention. Fig. Figure 4 is a curve diagram showing an impedance / frequency characteristic of the device for elastic waves according to the first embodiment. Fig. Figure 5 is a partially opened plan view of a main section of a device for elastic shafts according to a comparative example. Fig. Figure 6 is a curve diagram showing an impedance / frequency characteristic of the device for elastic waves according to the comparison example. Fig. Figure 7 is a curve diagram showing a relationship between a ratio of a sound velocity difference ΔV with reference to the sound velocity in a mean region and a dimension Y of a low sound velocity region in a longitudinal direction when a piston mode is provided, where the sound velocity difference ΔV is the difference between the sound velocity in the mean region and the sound velocity in the low sound velocity region. Fig. Figure 8 is a partially opened plan view of a main section of a device for elastic shafts according to a second embodiment of the present invention. Fig. Figure 9 is a partially opened plan view of a main section of a device for elastic shafts according to a third embodiment of the present invention. Fig. Figure 10 is a partially opened plan view of a main section of a device for elastic shafts according to a fourth embodiment of the present invention. Fig. Figure 11 is a partially opened plan view of a main section of a device for elastic shafts according to a fifth embodiment of the present invention. Fig. Figure 12 is a partially opened plan view of a main section of a device for elastic shafts according to a sixth embodiment of the present invention. Fig. Figure 13 is a partially opened plan view of a main section of a device for elastic shafts according to a seventh embodiment of the present invention. Fig. Figure 14 is a partially opened plan view of a main section of a device for elastic shafts according to an eighth embodiment of the present invention. Fig. Figure 15 is a partially opened plan view of a main section of a device for elastic shafts according to a ninth embodiment of the present invention. Fig. Figure 16 is a partially opened plan view of a main section of a device for elastic shafts according to a tenth embodiment of the present invention. Fig. Figure 17 is a schematic front sectional view of a device for elastic shafts according to a modification of the first embodiment of the present invention. Fig. Figure 18 is a curve diagram showing a relationship between the specific volume resistivity of Si serving as a material for a high speed of sound support substrate and the amount of change in insertion loss. Fig. Figure 19 is a curve diagram showing a relationship between the specific volume resistance of Si, which serves as a material of the high speed of sound support substrate, and the amount of change in the steepness of the filter characteristic curve. Fig. Figure 20 is a curve diagram showing a change in the frequency difference when the film thickness of Al is changed. Fig. Figure 21 is a curve diagram showing a change in insertion loss when the film thickness of Al is changed. Fig. Figure 22 is a curve diagram showing a relationship between the film thickness of a LiTaO3 film and Q in the elastic wave apparatus. Fig. Figure 23 is a curve diagram showing a relationship between the film thickness of the LiTaO3 film and a temperature coefficient of the resonance frequency TCF in the device for elastic waves. Fig. Figure 24 is a curve diagram showing a relationship between the film thickness of the LiTaO3 film and the speed of sound in the elastic wave apparatus. Fig. Figure 25 is a curve diagram showing a relationship between the thickness of a piezoelectric film made of LiTaO3 and a relative band. DESCRIPTION OF EXECUTION FORMS

[0021] Specific embodiments of the present invention are described below with reference to the drawings in order to explain the present invention.

[0022] The embodiments described in the description are exemplary representations. The structures according to the embodiments can be partially replaced by structures according to different embodiments or combined with structures according to different embodiments.

[0023] Fig. Figure 1 is a partially opened plan view of a main section of a device for elastic shafts according to a first embodiment of the present invention. Fig. Figure 2 is a schematic front sectional view of it. Fig. Figure 3 is a schematic plan view of the device for elastic shafts according to the first embodiment.

[0024] As in Fig. As shown in Figure 2, an elastic wave device 1 includes a high-speed sound support substrate 7, which serves as the high-speed sound material. The high-speed sound support substrate 7 is made of silicon. A low-speed sound film 8, in which the sound speed is relatively low, is laminated onto the high-speed sound support substrate 7. A piezoelectric film 9 is laminated onto the low-speed sound film 8. An IDT electrode 3 is laminated onto a top surface of the piezoelectric film 9. The IDT electrode 3 can also be laminated onto a bottom surface of the piezoelectric film 9.

[0025] In this embodiment, the piezoelectric film 9 consists of a 50° YX LiTaO3 film. If, for example, the electromagnetic coupling coefficient of the piezoelectric film 9 is relatively large, as is the case with LiNbO3 and LiTaO3, the piezoelectric film 9 can also consist of other piezoelectric monocrystals or piezoelectric ceramics. The cutting angle is also not limited to 50° Y. In this embodiment, the thickness of LT is 0.3 λ.

[0026] The low-speed sound film 8 consists of a material in which the speed of sound of a volume wave in the low-speed sound film is lower than that of an elastic wave propagating through the piezoelectric film 9. In this embodiment, the low-speed sound film 8 consists of SiO2. In this embodiment, the film thickness of SiO2 is 0.35 λ.

[0027] As long as the above-mentioned conditions are met, the material of the low sound film 8 is not limited to specific materials. Therefore, the low sound film 8 can be made from a dielectric material such as various types of glass or ceramics, for example silicon oxide (e.g., SiO2), silicon nitride, aluminum oxide, silicon carbide, or zirconium oxide, or it can be made from a semiconductor such as silicon or gallium nitride.

[0028] In the description, the term "high-speed sound material" refers to a layer in which the speed of sound of a volume wave propagating through the piezoelectric film is higher than that of an elastic wave, such as a surface wave or a limiting wave. The term "low-speed sound film" refers to a film in which the speed of sound of a volume wave propagating through the piezoelectric film is lower than that of an elastic wave propagating through the piezoelectric film. The IDT electrode with a specific structure excites elastic waves of different modes, each exhibiting different speeds of sound. An "elastic wave propagating through the piezoelectric film" refers to an elastic wave in a specific mode used to obtain filter and resonator characteristics.A “mode” of the volume wave, which determines the speed of sound of the volume wave, is defined according to a mode of use of the elastic wave propagating through the piezoelectric film.

[0029] The high-speed sound support substrate 7 serves to confine a surface sound wave within a section where the piezoelectric film 9 and the low-speed sound film 8 are laminated, and to prevent the surface sound wave from escaping into a structure beneath the high-speed sound support substrate 7. In this embodiment, the high-speed sound support substrate 7 is made of silicon. Various types of high-speed sound materials can be used, provided the surface sound wave can be confined. Examples include aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, a DLC film, and diamond; a medium whose main component is one of the materials mentioned above; and a medium whose main component is a mixture of the materials mentioned above.

[0030] In order to enclose the surface sound wave in the section where the piezoelectric film 9 and the low sound velocity film 8 are laminated, it is desirable that the high sound velocity material be thick and at least 0.5 times the wavelength λ of the surface sound wave, and particularly preferably at least 1.5 times the wavelength λ of the surface sound wave.

[0031] It is desirable that the specific volume resistivity of the aforementioned high-speed sound support substrate be 1000 Ωcm or higher. By using silicon, which has a high electrical resistivity, it is possible to obtain even better resonance and filter characteristics. Fig. Figure 18 shows a relationship between the specific volume resistivity of Si, which is a material of the high-speed sound support substrate, and the magnitude of the change in insertion loss. Fig. In Figure 18, the horizontal axis denotes the specific volume resistivity of Si, and the vertical axis denotes the magnitude of the change in insertion loss in a transmission band. If the specific volume resistivity of the high-speed Si support substrate is reduced, the insertion loss increases and worsens. The magnitude of the change in insertion loss along the vertical axis represents the magnitude of the deterioration in insertion loss from a reference that corresponds to the insertion loss when the high-speed Si support substrate is an insulating material. As shown in Figure 18, the following applies: Fig. As can be seen in Figure 18, the deterioration of the insertion loss can be avoided if the specific volume resistivity of Si is 1000 Ωcm or more. Consequently, it is possible to obtain a good filter characteristic. Therefore, it is desirable that the specific volume resistivity of the high-speed sound support substrate, which consists of Si, be 1000 Ωcm or more.

[0032] Fig. Figure 19 is a curve diagram showing a relationship between the specific volume resistivity of Si, which is a material of the high-speed sound support substrate, and the amount of change in the slope of the filter characteristic. Fig. In Figure 19, the horizontal axis denotes the specific volume resistivity of Si, and the vertical axis denotes the magnitude of the change in the slope of the filter characteristic. The magnitude of the change in the slope of the filter characteristic refers to the magnitude of the change in the slope of the filter characteristic compared to a reference that corresponds to the slope of the filter characteristic when the high-speed sound support substrate is an insulating material. Here, the slope of the filter characteristic, at a passband shoulder, refers to the difference between the frequency at which the attenuation is 3.5 dB and the frequency at which the attenuation is 40 dB. As the frequency difference decreases, the slope increases. As from Fig. As can be seen in Figure 19, the change in slope can be avoided if the specific volume resistivity of Si is 4000 Ωcm or more. Consequently, it is possible to obtain an even better filter characteristic. Therefore, it is desirable that the specific volume resistivity of the high-speed sound support substrate, which consists of Si, be 4000 Ωcm or more.

[0033] The specific volume resistivity of Si is usually 100 × 10 3 Ωcm or less.

[0034] Instead of the high-speed sound support substrate 7, a high-speed sound film 7b laminated onto a support substrate 7a can be used as the high-speed sound material, as in the case described in Fig. Modification 17 shown. In this case, a suitable material can be used as the support substrate 7a. Examples of such materials include piezoelectric materials, such as sapphire, LiTaO3, LiNbO3, and crystals; dielectric materials, such as various types of glass and ceramics, such as aluminum oxide, magnesium oxide, silicon nitride, aluminum nitride, silicon carbide, zirconium oxide, cordierite, mullite, steatite, and forsterite; semiconductors, such as silicon and gallium nitride; and resin substrates.

[0035] In the elastic wave device 1, the low-speed sound film 8 is positioned between the high-speed sound support substrate 7 and the piezoelectric film 9. This reduces the speed of sound of the elastic wave. Conversely, the energy of the elastic waves is essentially concentrated in a low-speed sound medium. Therefore, it is possible to increase the effect of trapping the energy of the elastic waves within the piezoelectric film 9 and the IDT electrode 3. Consequently, compared to the case where such a low-speed sound film 8 is not present, it is possible to reduce loss and increase the efficiency. As shown in the diagram... Fig. As can be seen in Figure 22, when the film thickness of LiTaO3 is 3.5 λ or less, the quality factor is higher, and the Q-characteristics are better than those where the film thickness of LiTaO3 is greater than 3.5 λ. Fig. Figure 23 shows that when the film thickness of LiTaO3 is 2.5 λ or less, the absolute value of the temperature coefficient of the resonance frequency (TCF) can be designed to be smaller than when the absolute value of the temperature coefficient of the resonance frequency (TCF) is greater than 2.5 λ. Particularly preferably, in the range of 2 λ or less, the absolute value of the temperature coefficient of the resonance frequency (TCF) can be designed to be -10 ppm / °C or less, which is desirable. Furthermore, it shows Fig. 24, that if the film thickness of LiTaO3 is 1.5 λ or less, the speed of sound is reduced. Therefore, the size of the IDT electrode is reduced to obtain a desired frequency, so that a device can be miniaturized. Furthermore, as from Fig. 25 can be seen when the film thickness of LiTaO3 is 0.5 λ or less, a specific band is increased.

[0036] The high-speed sound support substrate 7 prevents the escape of an elastic wave into a layer below the high-speed sound support substrate 7.

[0037] Although in this embodiment the low sound velocity film 8 and the high sound velocity support substrate 7, which serves as a high sound velocity material, are laminated to a bottom side of the piezoelectric film 9, several of the low sound velocity films and several of the high sound velocity materials can also be provided by lamination.

[0038] Fig. Figure 2 schematically illustrates an electrode structure containing the IDT electrode 3. As shown in Fig. As shown in Figure 3, in the elastic wave device 1, reflectors 4 and 5 are arranged on respective sides of the IDT electrode 3 in one direction of propagation of a surface sound wave. That is, the elastic wave device 1 is a single-port surface sound wave resonator.

[0039] Fig. Figure 3 schematically illustrates the IDT electrode 3 by a symbol containing an X surrounded by a rectangular frame. Details of the IDT electrode 3 are described with reference to Fig. 1 described.

[0040] IDT electrode 3 is a standard IDT electrode that is not subjected to apodization weighting. The electrode finger period is 2.0 µm. The electrode finger period of the IDT electrode is not limited to specific periods. The number of electrode finger pairs is 150, and a crossing section measures 10 λ (λ being the wavelength of an elastic wave excited at the IDT electrode). Reflectors 4 and 5 are grating reflectors with their two ends short-circuited. The number of electrode fingers on reflectors 4 and 5 is 20.

[0041] In this embodiment, the IDT electrode 3 and the reflectors 4 and 5 are formed from a multilayer metal film comprising a titanium film and an aluminum film laminated onto the titanium film. The thickness of the titanium film is 10 nm, and the thickness of the aluminum film is 167 nm. In the multilayer metal film, the aluminum film is the predominant film and has a thickness of 167 nm = 0.0835 λ.

[0042] The metals used to construct the IDT electrode 3 are not limited to these metals. Suitable metals or alloys can be used.

[0043] As mentioned above, the thickness of the IDT electrode, whose main component is Al, is 0.0835 λ. However, according to an experiment carried out by the authors of the present application, it is desirable for the thickness to be 0.08 λ or more. That is, when a filter for elastic waves is formed as the device for elastic waves, it is possible to increase the steepness of the filter characteristic.

[0044] Fig. Figure 20 is a curve showing the change in the frequency difference when the film thickness of Al is varied. This frequency difference is a frequency difference at a passband shoulder and is the difference between the frequency at which the attenuation is 3.5 dB and the frequency at which the attenuation is 40 dB. As the frequency difference decreases, the slope at the shoulder increases.

[0045] As from Fig. As can be seen in Figure 20, when the thickness of the aluminum film becomes less than 0.08 λ, the frequency difference increases considerably as the film thickness decreases. Conversely, when the aluminum film thickness is 0.08 λ or greater, the frequency difference is essentially constant and small. Therefore, it is desirable for the film thickness of the aluminum film to be 0.08 λ or greater.

[0046] Furthermore, it is desirable that the film thickness of the IDT electrode 3 be 0.1 λ or more. This makes it possible to reduce the electrical resistance of each electrode finger. Consequently, it is possible to reduce the loss.

[0047] Fig. Figure 21 is a curve diagram showing the change in insertion loss when the film thickness of the aluminum film is varied. Insertion loss refers to a minimum insertion loss, with the insertion loss being smallest in a passband.

[0048] As from Fig. As can be seen in Figure 21, if the film thickness of the Al film is 0.10 λ or more, the insertion loss is sufficiently small such that variations in the insertion loss are small when the film thickness of the Al film is varied. Therefore, the film thickness of the Al film is particularly preferably 0.10 λ or more. Since it is difficult to produce Al films when they are too thick, it is desirable that the film thickness be 400 nm or less. Therefore, it is desirable that the film thickness of the IDT electrode be 400 nm or less.

[0049] An SiO2 film can be formed in such a way that it contains Fig. The electrode structure shown in section 1 is covered. This makes it possible to improve the frequency-temperature characteristic.

[0050] The device for elastic shafts 1 according to this embodiment has a structure that prevents transverse mode ripple by providing a piston mode at the IDT electrode 3. This is described with reference to Fig. 1 described.

[0051] The IDT electrode 3 contains a first busbar 11 and a second busbar 12, which is arranged separately from the first busbar 11. The first busbar 11 and the second busbar 12 extend parallel to the direction of propagation of a surface sound wave.

[0052] The proximal ends of several first electrode fingers 13 are connected to the first busbar 11. The distal ends of the several first electrode fingers 13 extend from the first busbar 11 towards the second busbar 12. This means that the several first electrode fingers 13 extend in a direction orthogonal to the propagation direction of a surface sound wave.

[0053] The proximal ends of several second electrode fingers 14 are connected to the second busbar 12. The distal ends of the several second electrode fingers 14 extend from the second busbar 12 towards the first busbar 11. That is, the several second electrode fingers 14 also extend in a direction orthogonal to the propagation direction of a surface sound wave.

[0054] The multiple first electrode fingers 13 and the multiple second electrode fingers 14 are arranged between adjacent second electrode fingers 14 or adjacent first electrode fingers 13. Each first electrode finger 13 contains wide sections 13a, 13b, 13c, and 13d. Each second electrode finger 14 also contains wide sections 14a, 14b, 14c, and 14d. The shapes of the wide sections 13a to 13d and the wide sections 14a to 14d are described, with the shape of wide section 13a being described in such a way that it represents the shapes of the other wide sections. Each wide section 13a has a dimension in a lateral direction, that is, a dimension in the propagation direction of a surface sound wave, which is larger than that of any remaining section of the corresponding first electrode finger 13.

[0055] In this embodiment, each wide section 13a has the shape of an isosceles trapezoid projecting from the lateral edges of the corresponding electrode finger 13 in the propagation directions of a surface sound wave. The shape of each wide section is not limited to this, so that projections of various other shapes, such as semicircular projections, can be arranged to project from the lateral edges of the corresponding electrode fingers 13 in the propagation directions of a surface sound wave.

[0056] The wide sections 13a and 13b of each first electrode finger 13 are positioned towards the side of the proximal end of the corresponding first electrode finger 13. In other words, the wide sections 13a and 13b are positioned towards the side of the first busbar 11, and the wide sections 13c and 13d are positioned towards the side of the distal end of the corresponding first electrode fingers 13, that is, towards the side of the second busbar 12.

[0057] The wide sections 14a and 14b of each second electrode finger 14 are positioned towards the distal end of the corresponding second electrode finger 14. The wide sections 14a and 14b and the wide sections 13a and 13b are arranged alternately in a region near the corresponding first busbar 11 in a direction orthogonal to the propagation direction of a surface sound wave, i.e., in the direction in which the electrode fingers extend. Likewise, the wide sections 13c and 13d and the wide sections 14c and 14d are arranged alternately on the side near the second busbar 12 in the direction in which the electrode fingers extend.

[0058] In a region where the wide-width sections 13a and 13b and the wide-width sections 14a and 14b are provided, a Fig. Region 1 shown: V2 trained. V1 to V6 on the right side. Fig. Regions 1 are arranged towards the outside of the center of the IDT electrode 3 in a direction orthogonal to the propagation direction of a surface sound wave. The velocities V1 to V6 of an elastic wave propagating through regions V1 to V6 (hereinafter referred to as sound velocities) are schematically represented in Fig. Figure 1 shows the speed of sound in a region Vn (where n is a natural number). In the following description, the speed of sound in a region is defined as V. n Designated as such. Here, region V1 is an IDT mid-region located between the wide-latitude sections 13b and the wide-latitude sections 13c.

[0059] The speed of sound in region V2, where the wide-width sections 13a, 13b, 14a and 14b are provided, is lower than the speed of sound in region V1 in the IDT center.

[0060] In this embodiment, projections 13e, extending in the transverse direction of the electrode fingers, are formed at the proximal ends of the corresponding electrode fingers 13. Therefore, the speed of sound in region V3, where the projections 13e are located, is lower than the speed of sound in region V5 of a section with a high speed of sound (which will be described later). Since the second electrode fingers 14 are not present in region V3, the speed of sound V3 in region V3 is higher than the speed of sound V2 in region V2.

[0061] As described above, JP 2011-101350 A and WO 2011 / 088904 A1 each describe structures containing a low sound velocity region V2, resulting from the arrangement of the wide sections 13a, 13b, 14a and 14b. Similarly, a region V2 is also present on the second busbar 12 where the wide sections 13c, 13d, 14c and 14d are provided.

[0062] In this embodiment, the first busbar 11 comprises an inner busbar section 11A, a middle busbar section 11B, and an outer busbar section 11C. Here, in the direction in which the electrode fingers of the IDT electrode 3 extend, the term "inner" refers to a side where the first electrode fingers 13 and the second electrode fingers 14 are located, and the term "outer" refers to an opposite side.

[0063] The inner busbar section 11A is a section to which the proximal ends of the multiple first electrode fingers 13 are connected. In this embodiment, the inner busbar section 11A has the form of a long and narrow band extending in the direction of propagation of a surface sound wave. Since this is a metallized section, the inner busbar section 11A forms the low sound velocity region V4.

[0064] Several cavities 15 are distributed in the central busbar section 11B along the propagation directions of a surface sound wave. In this embodiment, the cavities 15 are positioned between corresponding connecting sections 16 and 16, which extend in the same direction as the electrode fingers. In this embodiment, the width of the connecting sections 16 is the same as the width of the first electrode fingers 13, and the connecting sections 16 extend along extension lines from the first electrode fingers 13. The dimensions and positions of the connecting sections 16 are not limited thereto. Although the cavities 15 have rectangular shapes in this embodiment, their shapes are not restricted to rectangular forms.

[0065] On the central busbar section 11B, the connecting sections 16 and the cavities 15 are arranged alternately along the propagation direction of a surface sound wave. Because there are many sections that are not metallized, the central busbar section 11B therefore forms the high-speed sound region V5. The outer busbar section 11C has no cavities. Therefore, the outer busbar section 11C is a metallized region, and region V6 is a low-speed sound region.

[0066] Similarly, the second busbar 12 contains an inner busbar section 12A, a middle busbar section 12B, and an outer busbar section 12C. The corresponding sections are given the same reference numbers and are not described.

[0067] Since the IDT electrode 3 in the elastic wave device 1 has the structure described above, the low-speed sound regions are located on the outside of the central region V1, and the high-speed sound region V5 is located on the outside of regions V2 to V4, which are low-speed sound regions. Therefore, it is possible to provide a piston mode and effectively suppress transverse mode ripple. Furthermore, it is possible to effectively contain an elastic wave. This will be explained in detail with reference to the Fig. 4 to 7 described.

[0068] Fig. Figure 4 is a curve diagram showing an impedance-frequency characteristic of the device for elastic waves according to the first embodiment. Fig. Figure 6 is a curve diagram showing the impedance-frequency characteristic of an elastic wave device according to a comparative example. The main section of an IDT electrode of the elastic wave device according to the comparative example is shown with reference to Fig. 5 described. As in Fig. As shown in Figure 5, in the comparative example, a first busbar 1011 contains only a thick, ribbon-shaped metallized region. That is, in the comparative example, unlike the embodiment described above, there is no central busbar section 11B with multiple cavities 15. Therefore, the section where the first busbar 1011 is located is a low-speed sound region, designated V14.

[0069] In the comparative example, the ones in Fig. The projections shown in Figure 13e are not formed. The other structural features according to the comparative example are the same as those according to the embodiment described above. Sound velocities V 11 to V 14 In the respective regions V11 to V14, in the direction in which the electrode fingers of the IDT electrode of the device for elastic waves extend according to the comparative example, are schematically shown on the right-hand side. Fig. 5 shown.

[0070] As by comparing Fig. 4 and Fig. 6 becomes clear, appear in Fig. Six strong ripples appear between the resonant frequency and the antiresonant frequency, and in a region where the frequencies are higher than the antiresonant frequency. These ripples are called transverse mode ripples. In contrast, in Fig. 4 such ripples not.

[0071] In the embodiment described above, the sound velocities V1 to V6 in the respective regions V1 to V6 are as described in Fig. 1 shown. That is, since the inner busbar section 11A is present in addition to the wide sections 13a, 13b, 14a and 14b, the average value of the sound velocities in regions V2, V3 and V4, which are low sound velocity regions, is effectively reduced.

[0072] Therefore, the difference in sound velocity ΔV between the speed of sound in a low-speed region and the speed of sound in the middle region is very large. Consequently, it is possible to effectively suppress transverse mode ripple. That is, if the difference in sound velocity ΔV is increased, the piston mode is reliably provided, making it possible to effectively suppress transverse mode ripple.

[0073] Fig. Figure 7 is a curve diagram showing a relationship between a ratio of the sound velocity difference ΔV with respect to the sound velocity in the middle region and a dimension Y of a low sound velocity region in a longitudinal direction in which the electrode fingers extend, when the conditions for providing a piston mode are met, where the sound velocity difference ΔV is the difference between the sound velocity of the middle region and the sound velocity of the low sound velocity region. As shown from Fig. As can be seen in Figure 7, if the dimension Y of the low-speed region is small in the longitudinal direction in which the electrode fingers extend, the speed of sound difference ΔV between the speed of sound in the middle region and the speed of sound in the low-speed region, which is required to provide the piston mode, is increased. To provide an ideal piston mode that can suppress all transverse mode ripples, it is desirable for the dimension Y to be small. That is, it is desirable for the speed of sound difference ΔV between the speed of sound in the middle region and the speed of sound in the low-speed regions to be large.

[0074] Since a region with a low speed of sound contains only sections of large width, the difference in the speed of sound between the speed of sound in the middle region and the speed of sound in the region with a low speed of sound in the structure can be determined according to the equation in Fig. The comparative example shown in section 5 cannot be designed to be so large. Therefore, to provide the piston mode, dimension Y must be large. However, in this case, the ideal piston mode cannot be provided. This is why, as shown in Fig. 6 shown, to transverse mode ripple.

[0075] In contrast, in the structure according to this embodiment, since the inner busbar section 11A is present, the difference in the speed of sound ΔV between the speed of sound in the middle region and the speed of sound in the low-speed region can be designed to be large, and the dimension Y required for providing the piston mode can be designed to be small. Therefore, it is possible to provide the ideal piston mode. Consequently, as in Fig. Figure 4 shows that it is possible to effectively suppress the transverse mode ripple.

[0076] Experiments conducted by the inventors of the present application have confirmed that it is desirable for the metallization ratio of the electrode fingers to be in the range of 0.6 to 0.9 in sections where, for example, the wide sections 13a, 13b, 14a and 14b are formed. Since the metallization ratio is increased, the sound velocity difference ΔV can be designed to be large. Due to process-related limitations, it is desirable for the metallization ratio to be 0.9 or less.

[0077] In this embodiment, it is desirable that the distance between the distal ends of the second electrode fingers 14 and the first busbar 11 along a direction orthogonal to the propagation direction of a surface sound wave, i.e., the size of a gap indicated by region V3 between the distal ends of the electrode fingers and the corresponding busbar, be small. To reduce the dimensions of region V3, there are process-related limitations. Experiments carried out by the authors of the present application have revealed that when the wavelength of a surface sound wave is λ, the distance is preferably 0.5 λ or less, and particularly preferably 0.25 λ or less.

[0078] Since the projections 13e and 14e are arranged, in this embodiment the dimension in the electrode finger width direction in region V3 is larger than the width of the electrode fingers 13 and 14 in region V1. Therefore, the following relationship applies: speed of sound V1 < speed of sound V3. The projections 13e and 14e need not be present. Therefore, the width of the electrode fingers 14 in region V3 can be equal to the width of the electrode fingers 14 in region V1, which is an intermediate region.

[0079] As with this embodiment, it is generally desirable for the projections 13e and 14e to be present in region V3 and for the speed of sound in region V3 to be further reduced. This means that the average value of the speeds of sound V2 to V4 as a whole can be further reduced in the respective regions V2 to V4, which are regions with low speeds of sound.

[0080] Region V4, where the inner busbar section 11A is located, is also a region with a low speed of sound. Here, as mentioned above, the speed of sound is effectively reduced because the entire inner busbar section 11A is metallized. The inner busbar section 11A has the form of a long and narrow strip. It is desirable that the dimension of the inner busbar section 11A in a direction orthogonal to the propagation direction of an elastic wave, that is, the width of the inner busbar section 11A, be 0.5 λ or less.

[0081] In this embodiment, the width of the connecting sections 16 of the central busbar section 11B is equal to the width of the electrode fingers 13 and 14 in region V1. The dimension in the lateral direction of the connecting sections 16 does not necessarily have to be equal to the dimension in the lateral direction of the electrode fingers 13 and 14.

[0082] The metallization ratio of the electrode fingers in region V1 is 0.5. In this embodiment, the width of the central busbar section 11B, which is a high-speed sound region, is 2.0 λ in a direction perpendicular to the propagation direction of an elastic wave. The high-speed sound region only needs to have a width that allows the energy of a surface sound wave excited by the IDT electrode to be sufficiently low at the outer busbar section 11C. If the width of the central busbar section 11B is 2.0 λ or more, the excitation by the outer busbar section 11C can be designed to be sufficiently low.

[0083] In this embodiment, as mentioned above, the wide sections 13a, 13b, 13c, and 13d and the wide sections 14a, 14b, 14c, and 14d are arranged. Regions V2 to V4, which are low-speed regions, and region V5, which is a high-speed region containing cavities 15, are arranged on the outside of region V1, which serves as a middle region. Since the sound velocity difference ΔV between the sound velocity in the middle region and the average of the sound velocities in the low-speed regions is very high, it is possible to effectively suppress transverse mode ripple. This is because, by increasing the sound velocity difference ΔV, a piston mode close to the ideal piston mode can be provided. Therefore, as described in Fig. Figure 4 shows that it is possible to effectively suppress a transverse mode interference component.

[0084] Fig. Figures 8 to 15 are partially opened plan views of main sections of devices for elastic shafts according to a second to a ninth embodiment of the present invention.

[0085] As with the in Fig. The second embodiment shown in 8 requires the elements shown in Fig. In the second embodiment, the projections 13e shown in Figure 1 are not arranged at the proximal ends of the first electrode fingers 13. Similarly, in the second embodiment, projections are not arranged at the proximal ends of the second electrode fingers 14.

[0086] In the second embodiment, each first electrode finger 13 contains a wide section 13a, while adjacent second electrode fingers 14 each contain two wide sections 14a and 14b. Around these, 1.5 pairs of projections are arranged. The relationship between the sound velocities V1 to V6 in the regions V1 to V6 is as shown on the right-hand side in Fig. Figure 8 shows that the speed of sound V3 and the speed of sound V5 are equal. In this embodiment as well, the average value of the speeds of sound V2 to V4 in regions V2 to V4, which are low-speed regions, is effectively lower than the speed of sound V1 in region V1, which is a medium-speed region. Therefore, as in the first embodiment, it is possible to effectively suppress transverse mode ripple. The other structural features according to the second embodiment are the same as those according to the first embodiment.

[0087] At the in Fig. In the third embodiment shown in Figure 9, a distal end of each second electrode finger 14 includes a wide section 14a on the side of a first busbar 11. The first electrode fingers 13 do not contain wide sections near sections where the wide sections 14a are formed. The other structural features are the same as those according to the first embodiment. The sound velocities V1 to V6 in regions V1 to V6 according to this embodiment are shown schematically on the right. Fig. Figure 9 shows that in this embodiment as well, the average value of the sound velocities V2 to V4 in regions V2 to V4 is effectively set lower than the sound velocity V1 in region V1, which is a middle region. Therefore, as in the first embodiment, it is possible to effectively suppress transverse mode ripple.

[0088] Only the first electrode fingers 13 or only the second electrode fingers 14 need to contain a wide section. The number of wide sections can be such that a single electrode finger contains only a single wide section 14a on the busbar 11 side.

[0089] In this embodiment, as with the wide sections 14a, a single wide section is arranged on the side of a distal end of each first electrode finger 13, and each second electrode finger 14 does not contain a wide section on the side of the second busbar 14.

[0090] At the in Fig. In the fourth embodiment shown in Figure 10, each first electrode 13 contains a wide section 13a, and each second electrode finger 14 contains a wide section 14a on the side of a first busbar 11. That is, in a region towards the side of the first busbar 11, to form a low-speed region, each electrode finger 13 contains a wide section 13a, and each electrode finger 14 contains a wide section 14a. The Fig. The projections 13e shown in Figure 1 are not formed at the proximal ends of the electrode fingers 13. The projections mentioned above are also not formed at the proximal ends of the second electrode fingers.

[0091] Also on the side of a distal end of each first electrode finger 13, that is, on the side of a second busbar, a single section of large width is arranged at the distal end of each first electrode finger and near a proximal end of each second electrode finger.

[0092] As in this embodiment, each electrode finger 13 and each electrode finger 14 can contain a wide section to effectively reduce the speed of sound V2 in a region with a low speed of sound V2. Also in this case, as in the first to third embodiments, it is possible to effectively suppress transverse mode ripple based on a piston mode principle.

[0093] As with the in Fig. In the fifth embodiment shown in Figure 11, the dimensions of each cavity 15 in a central busbar section 11B can be made large in the propagation direction of a surface sound wave. Here, the center-to-center distance between connecting sections 16 and 16 on respective sides of the corresponding cavity 15 is twice the period of the first electrode fingers 13 along the propagation direction of a surface sound wave. In this way, the shape of each cavity 15 is larger than that of each cavity in the first embodiment. The other structural features are the same as those according to the first embodiment. In this embodiment as well, it is possible to reliably contain an elastic wave while effectively suppressing transverse mode ripple, since a sound velocity V5 in a region V5, which is a region with a high sound velocity, can be effectively increased.More precisely, since the surface area of ​​each cavity is increased by 15, it is possible to increase the speed of sound V5 in the region V5 even more effectively.

[0094] At the in Fig. In the sixth embodiment shown in Figure 12, each connecting section 16 is positioned on an extension line from a distal end of a second electrode finger 14. In this way, each connecting section 16 can be arranged on the extension line from the corresponding second electrode finger 14 instead of on the extension line from the corresponding first electrode finger 13. In this case, to increase symmetry, it is desirable to provide the connecting sections on the extension lines from the distal ends of the first electrode fingers 13 on the side of a second busbar 12.

[0095] At the in Fig. In the seventh embodiment shown in Figure 13, the width of each connecting section 16, that is, the dimension of each connecting section 16 in the propagation direction of a surface sound wave, is smaller than that of the electrode fingers 13 and electrode fingers 14. The connecting sections 16 are arranged on extension lines from the first electrode finger 13 or the second electrode finger 14. Therefore, the size of each cavity 15 along the propagation direction of a surface sound wave is small. In this way, the arrangement of the connecting sections 16 can be changed as needed. As in the embodiment shown in Fig. In the eighth embodiment shown in 14, an electrode strip 16a, extending from an outer busbar section 11C and not reaching an inner busbar section 11A, can be used instead of the connecting sections 16 for each in Fig. The second connecting section 16 shown in Figure 13 is arranged along the direction of propagation of a surface sound wave. An electrode strip extending in a direction opposite to that in which the electrode strips 16a extend from the inner busbar section 11A towards the outer busbar section 11C and do not reach the outer busbar section 11C can be arranged.

[0096] Furthermore, as with the in Fig. In the ninth embodiment shown in Figure 15, the positions of several connecting sections 16 are offset in the propagation direction of a surface sound wave from extension lines of the electrode fingers 13 and electrode fingers 14.

[0097] Fig. Figure 16 is a partially opened plan view of a main section of an elastic wave device according to a tenth embodiment of the present invention. In the elastic wave device according to the tenth embodiment, first electrode fingers 13 and second electrode fingers 14 are arranged side by side in the propagation direction of a surface sound wave. Of the multiple first electrode fingers 13, the widths of electrode fingers 13X are larger than the widths of the other electrode fingers 13.More precisely, the width of an electrode finger 13X is equal to the width of the electrode finger 13 plus the dimension of a section between an electrode finger 13 and an electrode finger 14 in the propagation direction of a surface sound wave (that is, the width of this section) plus the width of the second electrode finger 14 plus the size of a gap between the second electrode finger 14 and a first electrode finger 13 in the propagation direction of a surface sound wave plus the width of the first electrode finger 13. In other words, the polarity of a single second electrode finger 14 is reversed and set as a first electrode finger 13.A structure in which a metal film used to form an electrode finger is embedded in a gap between the first electrode finger 13 formed by the polarity conversion and the first electrode finger 13 on both sides corresponds to an electrode finger 13X.

[0098] In the tenth embodiment, at least some of the electrode fingers in an IDT electrode 3 are electrode fingers 13X and are subjected to a pullback weighting. This means that, for example, if a filter for elastic waves is designed as a device for elastic waves, it is possible to increase the steepness of the filter characteristic.

[0099] As in the Fig.As shown in Figures 8 to 16, the shape of the cavities 15, the dimensions, the shape, the center-to-center spacing, etc., of the connecting sections 16 can be varied according to the present invention, as long as the speed of sound V5 in the region V5, which is a region with a high speed of sound, can be increased; and their structures are not limited to the structures illustrated.

[0100] As long as the average value of the sound velocities V2 to V4 in the regions V2 to V4, which are regions with low sound velocity, can be designed to be low, for example the shape and dimensions of the wide sections 13a, 13b, 14a and 14b can be changed as needed.

[0101] As mentioned above, in sections where electrode fingers 13 and 14 are adjacent, either electrode finger 13 or electrode finger 14 needs to contain a wide section, or both electrode fingers 13 and 14 may contain a wide section. Furthermore, a wide section need only be oriented towards the side of the proximal end of the middle region of each electrode finger or towards the side of the distal end of the middle region of each electrode finger. This means that the wide sections can be oriented towards at least one side of the proximal end and the other side of the distal end.

[0102] The number of wide-width sections in the low-speed sound region is not limited to one or two. Any number of wide-width sections can be used.

[0103] The present invention is applicable not only to a surface sound wave device, but also to various other types of elastic wave devices, such as a limiting sound wave device. Furthermore, the present invention is applicable not only to an elastic wave device having electrode shapes forming a single-port resonator, but also to various other types of elastic wave filters, such as capture filters and bandpass filters, i.e., chain filters and longitudinally coupled resonator-type filters. REFERENCE MARK LIST 1 Device for elastic shafts 2 Support substrate 3 IDT electrode 4, 5 reflector 7. High-speed sound support substrate 7a Support substrate 7b High-speed film 8 Low-speed film 9 piezoelectric film 11 first busbar 11A inner busbar section 11B middle busbar section 11C outer busbar section 12 second busbar 12A inner busbar section 12B middle busbar section 12C outer busbar section 13 first electrode finger 13a, 13b, 13c, 13d Wide section 13th lead 13X Electrode Fingers 14 second electrode finger 14a, 14b, 14c, 14d Wide section 14th lead 15 Cavity 16 Connecting section 16a Electrode strips 1011 first busbar V1 to V6 Region V11 to V14 Region

Claims

[1] Elastic wave device (1) comprising a piezoelectric film, comprising: a material with a high speed of sound (7) in which the speed of sound of a volume wave propagating through the material with the high speed of sound is higher than that of an elastic wave propagating through the piezoelectric film, and a low-speed sound film (8) laminated onto the high-speed sound material and in which the speed of sound of a volume wave propagating through the low-speed sound film is lower than that of the elastic wave propagating through the piezoelectric film, wherein the piezoelectric film (9) is laminated onto the low sound velocity film and wherein an IDT electrode (3) is formed on a top side of the piezoelectric film opposite the low-speed sound film (8), wherein the IDT electrode (3) comprises: a first busbar (11), a second busbar (12) arranged separately from the first busbar, several first electrode fingers (13) whose proximal ends are electrically connected to the first busbar (11) and whose distal ends extend towards the second busbar (12), and several second electrode fingers (14) whose proximal ends are connected to the second busbar (12) and whose distal ends extend towards the first busbar (11), wherein, if a direction orthogonal to a direction in which the first electrode fingers (13) and the second electrode fingers (14) extend is defined as a width direction, the first electrode fingers (13) or the second electrode fingers (14) or the first electrode fingers and the second electrode fingers (13, 14) are provided with electrode fingers containing a wide section (13a-d, 14a-d), wherein the wide sections have a dimension in the width direction that is greater than a dimension of the electrode fingers at their midpoint in the longitudinal direction, wherein the wide sections (13a-d, 14a-d) are arranged in an overlap region of the electrode fingers (13, 14) closer to at least one of the proximal end and the distal end than a middle region (V1), wherein at least one of the first busbar (11) and the second busbar (12) has several cavities (15) distributed in a longitudinal direction of the first busbar (11) or the second busbar (12), and wherein the first busbar (11) and the second busbar (12) each contain an inner busbar section (11A) which is positioned closer to one side of the first electrode fingers (13) or one side of the second electrode fingers (14) than the cavities (15) and which extends in the longitudinal direction of the first busbar (11) and the second busbar (12), a middle busbar section (11B) which has the cavities (15), and an outer busbar section (11C) which is positioned opposite the inner busbar section (11A), while the middle busbar section (11B) is arranged in between. [2] Device for elastic waves (1) according to claim 1, wherein each inner busbar section (11A) has the form of a band extending in a propagation direction of elastic waves. [3] Device for elastic shafts (1) according to claim 1 or claim 2, wherein the first electrode fingers (13) and the second electrode fingers (14) each contain the wide section (13a-d, 14a-d). [4] Device for elastic shafts (1) according to any one of claims 1 to 3, wherein the first electrode fingers (13) or the second electrode fingers (14) or the first electrode fingers and the second electrode fingers (13, 14) each contain several of the wide sections (13a-d, 14a-d). [5] Device for elastic shafts (1) according to any one of claims 1 to 4, wherein the IDT electrode (3) is a normal IDT electrode which is not subjected to apodization weighting. [6] Device for elastic waves (1) according to any one of claims 1 to 5, wherein, if a wavelength of a surface sound wave is λ, a distance between the distal end of each first electrode finger (13) and the second busbar (12) relative to the distal end of each first electrode finger and a distance between the distal end of each second electrode finger (14) and the first busbar (11) relative to the distal end of each second electrode finger is 0.5 λ or less. [7] Device for elastic waves (1) according to any one of claims 1 to 6, further comprising a support substrate (7a) supporting the high speed of sound material, wherein the high speed of sound material is a high speed of sound film (7b). [8] Device for elastic shafts (1) according to any one of claims 1 to 6, wherein the high speed of sound material is a high speed of sound support substrate (7). [9] Device for elastic waves (1) according to any one of claims 1 to 8, wherein the polarity of at least one electrode finger in the IDT electrode is reversed, and an electrode material is embedded in a gap between the electrode finger whose polarity has been reversed and adjacent electrode fingers on both sides. [10] Device for elastic shafts (1) according to any one of claims 1 to 9, wherein the IDT electrode (3) is made of Al or an alloy the main component of which is Al, and the electrode film thickness of the IDT electrode is 0.08 λ or more. [11] Device for elastic waves (1) according to any one of claims 1 to 10, wherein the film thickness of the IDT electrode (3) is 0.10 λ or more and 400 nm or less. [12] Device for elastic waves (1) according to any one of claims 1 to 11, wherein the high speed of sound material is a silicon substrate (7) and its specific volume resistivity is 1000 Dem or more. [13] Device for elastic waves (1) according to any one of claims 1 to 12, wherein the high speed of sound material is a silicon substrate (7) and its specific volume resistivity is 4000 Ωcm or more.

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