JP2020102662A - Elastic wave element - Google Patents

Abstract

To provide a SAW element that has reduced transverse mode ripple.SOLUTION: An elastic wave element comprises a piezoelectric film 2 and an IDT electrode 3. The IDT electrode 3 includes first electrode fingers 32a and second electrode fingers 32b, first dummy electrodes 35a, and second dummy electrodes 35b. The direction connecting the tips of the first electrode fingers 32a and the direction connecting the second electrode fingers 32b, and a propagation direction of a SAW form inclination angles. The widths of the first dummy electrodes 35a and the second dummy electrodes 35b are made larger than the widths in an intersection area of the first electrode fingers 32a and the second electrode fingers 32b. When a frequency determined by the periods of the first electrode fingers 32a and the second electrode fingers 32b is λ, the thickness of the piezoelectric film 3 is less than 1λ.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an acoustic wave device.

The following Patent Document 1 discloses a surface acoustic wave resonator in which an electrode made of Al is provided on a 15° rotated Y-cut X-propagation LiNbO ₃ film. In this surface acoustic wave resonator, the straight line connecting the tips of the first electrode fingers of the IDT electrode and the straight line connecting the tips of the second electrode fingers are inclined by about 18° to 72° with respect to the surface wave propagation direction. Has been done.

Further, Patent Document 2 discloses an acoustic wave device in which a high acoustic velocity film, a low acoustic velocity film, a LiTaO ₃ film and an IDT electrode are laminated in this order on a supporting substrate.

JP-A-2000-286663 International publication 2012/0866639

Patent Document 1 describes that the lateral mode reflected by one bus bar and the lateral mode reflected by the other bus bar cancel each other out, and the lateral mode can be suppressed.

Patent Document 2 presents the problem that transverse mode ripple appears even when a LiTaO ₃ film is used.

In recent years, it has been further required to provide an acoustic wave device that suppresses transverse mode ripple. The present disclosure has been made in view of such circumstances, and an object thereof is to provide an acoustic wave device that suppresses transverse mode ripples and has high phase characteristics.

An acoustic wave device according to an embodiment of the present disclosure includes a piezoelectric film and an IDT electrode. The IDT electrode is located on the piezoelectric film. The IDT electrode is connected to the first bus bar and the second bus bar which are spaced apart from each other, the plurality of first electrode fingers connected to the first bus bar, and the second bus bar, and alternates with the first electrode finger. A plurality of second electrode fingers that are interleaved with each other, and a first dummy electrode that is connected to the first bus bar and that faces the tip of the second electrode finger with a space therebetween, and is connected to the second bus bar. A second dummy electrode facing the tip of the first electrode finger with a space therebetween. Then, the direction connecting the tips of the first electrode fingers and the arrangement direction of the first electrode fingers and the second electrode fingers form an inclination angle. Further, the width of the second dummy electrode in the arrangement direction is larger than the width of the first electrode finger in the intersecting region where the first electrode finger and the second electrode finger intersect. The piezoelectric film has a wavelength of less than 1λ, where λ is a wavelength determined by the period of the first electrode fingers and the second electrode fingers.

3 is a plan view of the acoustic wave device 1. FIG. It is sectional drawing in the II-II line of FIG. FIG. 3A is a diagram showing the phase characteristics of the acoustic wave devices according to the example and the comparative example, and FIG. 3B is an enlarged view of a part of FIG. 3A. FIG. 4A is a diagram showing a phase characteristic of an acoustic wave device according to a comparative example, and FIG. 4B is an enlarged view of a part of FIG. 4A. It is a diagram which shows the phase characteristic of the elastic wave element which concerns on an Example and a comparative example. FIG. 6A is a diagram showing a phase characteristic of an acoustic wave device according to a comparative example, and FIG. 6B is an enlarged view of a part of FIG. 6A. FIG. 7A is a diagram showing a phase characteristic of an acoustic wave device according to a comparative example, and FIG. 7B is an enlarged view of a part of FIG. 7A. It is a diagram which shows the phase characteristic of the elastic wave element which concerns on an Example and a comparative example. It is a principal part enlarged view of the IDT electrode which concerns on a modification.

Hereinafter, an acoustic wave device according to an embodiment of the present disclosure will be described with reference to the drawings. Note that the drawings used in the following description are schematic, and the dimensions and ratios in the drawings do not always match the actual ones.

The acoustic wave element may be either upward or downward in any direction, but hereinafter, for convenience, a rectangular coordinate system xyz is defined, and the positive side in the z direction is the upper side, the upper side, the lower side, and the like. The term shall be used.

<Acoustic wave element 1>
A configuration of an acoustic wave element 1 (SAW element 1) using a SAW (Surface Acoustic Wave) as an example of the acoustic wave element according to the embodiment will be described.

1 is a schematic plan view of the SAW element 1, and FIG. 2 is a sectional view taken along line II-II of FIG.

The SAW element 1 includes a piezoelectric layer 2, an IDT electrode 3 provided on the upper surface 2A of the piezoelectric layer 2, reflector electrodes 4 provided on both sides of the IDT electrode 3 along the SAW propagation direction, and a support substrate 5. , Is provided.

As shown in FIG. 2, in the SAW element 1, the support substrate 5 is located on the lower surface 2B side of the piezoelectric layer 2. The piezoelectric layer 2 and the supporting substrate 5 are directly or indirectly bonded to each other. In this example, the intermediate layer 7 is interposed between the piezoelectric layer 2 and the support substrate 5.

In the present embodiment, the support substrate 5 is made of a material having a higher acoustic velocity than the acoustic velocity of the elastic wave (bulk wave) propagating in the piezoelectric layer 2. Examples of such materials include Si, sapphire, crystal, AlN, and the like.

A material having a smaller thermal expansion coefficient than the piezoelectric layer 2 may be used as the supporting substrate 5. Examples of such a material include Si and sapphire. In this case, expansion and contraction of the piezoelectric layer 2 due to temperature changes can be suppressed, and characteristic changes due to temperature changes can be reduced.

The intermediate layer 7 may be a material that bonds the piezoelectric layer 2 and the support substrate 5. Alternatively, a material having a sound velocity lower than that of the bulk wave propagating through the piezoelectric layer 2 may be used. An example of such a material is silicon oxide (SiOx).

The piezoelectric layer 2 is located on the intermediate layer 7. The piezoelectric layer 2 is composed of a piezoelectric single-crystal substrate made of lithium niobate (LiNbO ₃ :hereinafter, referred to as LN) crystal or lithium tantalate (LiTaO ₃ :hereinafter, referred to as LT) crystal. Specifically, for example, the piezoelectric layer 2 may be composed of a 36° to 54° Y-cut-X propagation LT substrate. The planar shape and various dimensions of the piezoelectric layer 2 may be set appropriately.

The thickness (z direction) of the piezoelectric layer 2 is less than 2p, where p is the distance between the centers of the electrode fingers 32 described later. In other words, the piezoelectric layer 2 has a thickness less than λ because λ corresponds to 2p, where λ is a wavelength determined by the period of the electrode fingers 32 described later.

The IDT electrode 3 is located on the upper surface 2A of the piezoelectric layer 2. For the IDT electrode 3, for example, Al or an alloy mainly containing Al may be used. Further, it may be formed by stacking layers made of a plurality of metal materials. As such a metal material, Cu, Mo, Ni and the like can be exemplified in addition to Al.

The IDT electrode 3 is located between two ports P1 and P2 connected to different potentials. The SAW element 1 functions as a so-called 1-port resonator in which a high frequency signal is input from the port P1 and a high frequency signal is output from the port P2. The IDT electrodes 3 have a plurality of electrode fingers 32 and are arranged so as to be repeatedly arranged in the x direction of the drawing.

The IDT electrode 3 is composed of a pair of comb-teeth electrodes 30 that mesh with each other. The comb-teeth electrode 30 includes two bus bars 31 facing each other, a plurality of electrode fingers 32 extending from each bus bar 31 to the other bus bar 31 side, and extending from each bus bar 31 to the other bus bar 31 side and the other bus bar 31. And a dummy electrode 35 facing the tip of the electrode finger 32 extending from. In the pair of comb-teeth electrodes 30, the electrode fingers 32 connected to the one bus bar 31 and the electrode fingers 32 connected to the other bus bar 31 mesh with each other in the propagation direction of the elastic wave (intersect each other). Are arranged). As described above, the IDT electrode 3 includes the plurality of electrode fingers 32, which are arranged along the SAW propagation direction. In other words, the array direction (x direction) of the electrode fingers 32 is the SAW propagation direction. In other words, the direction orthogonal to the extending direction (long side direction) of the electrode fingers 32 is the array direction of the electrode fingers 32 and the SAW propagation direction.

The pitch of the electrode fingers 32 may be substantially the same, or may be provided with a changing portion for decreasing or increasing the pitch on a part of the side closer to the reflector electrode 4. The changing portion is 10% or less of the entire IDT electrode 4.

Here, for convenience, the bus bar 31 on the port P1 side is referred to as a first bus bar 31a, and the bus bar 31 on the port P2 side is referred to as a second bus bar 31b. Further, the electrode finger 32 and the dummy electrode 35 connected to the first bus bar 31a are referred to as a first electrode finger 32a and a first dummy electrode 35a, respectively. Similarly, the electrode finger 32 and the dummy electrode 35 connected to the second bus bar 31b are referred to as the second electrode finger 32b and the second dummy electrode 35b, respectively.

Then, the direction connecting the tips of the first electrode fingers 32a and the arrangement direction form an inclination angle. Specifically, the IDT electrode 3 is inclined such that the angle A1 formed by the virtual line L1 connecting the tips of the first electrode fingers 32a and the x-axis that is the arrangement direction is the inclination angle. Hereinafter, the angle A1 may be referred to as the first tilt angle.

In this example, both the direction connecting the tips of the second electrode fingers 32b and the arrangement direction are inclined so as to form an inclination angle. Specifically, the IDT electrode 3 is inclined such that the angle B1 formed by the virtual line L2 connecting the tips of the second electrode fingers 32b and the x-axis that is the arrangement direction is the inclination angle. Hereinafter, the angle B1 may be referred to as the second tilt angle.

Although the angle A1 and the angle B1 may be different, they are the same in this example. The shape formed by the intersecting region of the first electrode finger 32a and the second electrode finger 32b, that is, the virtual lines L1 and L2 and the electrode finger 32 located on the reflector 4 side is a parallelogram. There is. In this example, the outer shape of the IDT electrode 3 has a parallelogram shape, but only the intersecting region may have a parallelogram shape.

The bus bar 31 is, for example, formed in a long shape that extends linearly with a substantially constant width. Therefore, the edges of the bus bars 31 on the opposite sides are linear. The plurality of electrode fingers 32 are, for example, formed in a long shape that extends linearly with a substantially constant width, and are arranged at substantially constant intervals in the SAW propagation direction.

The width of the bus bar 31 does not have to be constant. It suffices that the edges on the opposite sides (inner sides) of the bus bar 31 be linear, and for example, the edges on the inner side may have a trapezoidal base.

The width w1 of each electrode finger 32 in the SAW propagation direction is appropriately set according to the electrical characteristics required for the SAW element 1. The width w1 of the electrode finger 32 is, for example, not less than 0.3 times and not more than 0.7 times the pitch p. That is, the duty is 0.3 to 0.7.

The width w1 of the electrode finger 32 is a value in the vicinity of the center of the intersecting region where the first electrode finger 32a and the second electrode finger 32b intersect each other.

The width w2 of the second dummy electrode 35b is thicker than the width w1. In this example, in addition to the second dummy electrode 35b, the width w3 of the first dummy electrode 35a is set to be equal to the width w2 and larger than the width w1. Furthermore, the first dummy electrode region, which is a region closer to the first bus bar 31a than the virtual line L3 connecting the tips of the first dummy electrodes 35a, and the second bus bar 31b side than the virtual line L4 connecting the tips of the second dummy electrodes 35b. The widths of the first electrode fingers 32a and the second electrode fingers 32b located in the second dummy electrode area which is the area of are also made equal to the width w2. That is, the width of the base portion of the electrode finger 32 is thick. With such a configuration, transverse mode spurious can be reduced. Hereinafter, the spurious reduction effect of this configuration will be verified.

The resonator characteristics of the SAW element 1 will be described. The design parameters of the SAW element 1 (Example 1) are as follows.

Piezoelectric layer 2 material: Y-cut X-propagation LT with a cut angle of 46°
Thickness of the piezoelectric layer 2: 0.8p
Crossing width of IDT electrode 3: 20λ
The number of electrode fingers of the IDT electrode 3 is 200: Duty in the first dummy electrode region and the second dummy electrode region of the IDT electrode 3 is 0.70
Duty: 0.53 in the intersection area of the IDT electrodes 3
Length of dummy electrode 35: 4p
Inclination angle: 6° (A1=B1)
Material of the intermediate layer 7: Silicon oxide Thickness of the intermediate layer 7: 0.3 p
The pitch p of the IDT electrodes 3 was 1 μm.

A SAW element of Comparative Example 1 was manufactured according to the above design parameters, except that the Duty in the first dummy electrode region and the Duty in the second dummy electrode region were equal to the Duty in the intersecting region.

FIG. 3A shows the phase characteristics of the resonators of Example 1 and Comparative Example 1. 3(b) shows an enlarged view of FIG. 3(a). 3A and 3B, the horizontal axis represents frequency (unit: MHz) and the vertical axis represents phase (unit: °). It is shown that between the resonance frequency and the anti-resonance frequency shown in FIG. 3B, the loss can be reduced as the phase approaches 90°. In FIG. 3, the characteristics of Example 1 are shown by a solid line, and the characteristics of Comparative Example 1 are shown by a broken line.

As is clear from FIG. 3, it can be confirmed that Example 1 can reduce the loss in the vicinity of the resonance frequency as compared with Comparative Example 1. As described above, by reducing the ripples in the vicinity of the resonance frequency where the power consumption is highest, the power resistance can be improved.

FIG. 4 shows phase characteristics when the tilt angle is changed from −6° to +6° in the SAW element of Comparative Example 1 as Comparative Example 2. Specifically, the inclination angle of Comparative Example 2-1 is −6°, the inclination angle of Comparative Example 2-2 is −4°, the inclination angle of Comparative Example 2-3 is 0°, and the inclination angle of Comparative Example 2-4. Was 4°, and the inclination angle of Comparative Example 2-5 was 6°. In addition, in FIG. 4, the characteristics of Comparative Examples 2-1 to 2-5 are sequentially shown by a solid line, a dotted line, a broken line, a one-dot chain line, and a long two-dot chain line.

FIGS. 4A and 4B are diagrams corresponding to FIGS. 3A and 3B, respectively. As is clear from this figure, the ripples that are often confirmed in the frequency range between the resonance frequency and the anti-resonance frequency when the tilt angle is 0° are reduced by tilting the IDT electrode 3. Actually, the phase characteristic is confirmed by swinging the tilt angle further. As a result, it was found that by setting the inclination angle to |6°±1°|, the transverse mode ripple can be effectively reduced in the state where the maximum phase between the resonance frequency and the antiresonance frequency is high. However, it can be confirmed that the ripple in the vicinity of the resonance frequency cannot be reduced even in the SAW element having the tilt angle of +6° which has the best phase characteristic in Comparative Example 2 (Comparative Example 1).

On the other hand, in the SAW element 1 according to the first embodiment, the ripple that could not be reduced only by tilting the IDT electrode 3 is compared with the line width of the dummy electrode 35 in comparison with the line width of the electrode finger 32 in the intersecting region. It has been confirmed that the thickness can be reduced by increasing the thickness.

The positive/negative of the tilt angle is determined by the direction with respect to the X axis which is the crystal axis of the piezoelectric layer 3. That is, when the coordinate axes are displayed in the right-handed system, the case of tilting in the counterclockwise direction in plan view is defined as tilting in the + direction.

<Duty>
Next, in the SAW element 1 of Example 1, the phase characteristic was measured when the line width of the dummy electrode 35 was changed with respect to the line width of the electrode finger 32 in the intersecting region. Specifically, the duty in the intersection area is 0.53, whereas the duty in the dummy areas (first dummy area and second dummy area) is changed from 0.53 to 0.70. Specifically, the duty in the dummy area is changed to 0.53, 0.57, 0.61, 0.66, and 0.70, and the comparative example 1, the example 1-1, and the example 1-2 are sequentially arranged. The phase characteristics were measured as Example 1-3 and Example 1-4.

FIG. 5 shows the result of the measurement thus performed. FIG. 5 is a diagram corresponding to FIG. In FIG. 5, the characteristics of Comparative Example 1 and Comparative Examples 1-1 to 1-4 are sequentially shown by a solid line, a dotted line, a broken line, a one-dot chain line, and a long two-dot chain line, respectively. As is clear from FIG. 5, it was confirmed that the ripple near the resonance frequency can be reduced by increasing the duty in the dummy region. In particular, the ripple can be almost eliminated by increasing the Duty in the intersection region by 0.08 or more. Further, although the loss can be reduced as the duty is increased, the duty may be 0.7 or less in order to reduce a short circuit with the other adjacent electrode fingers 32 or the dummy electrode 35. That is, it may be larger than the duty of the intersection region in the range of 0.16 or less. This value is 1.15 to 1.32 times in terms of the duty based on the duty in the intersection area.

In addition, when the duty in the dummy region is further increased to more than 0.7, the spurious of the stop band on the higher frequency side than the antiresonance frequency shifts toward the antiresonance frequency side, and the spurious intensity also increases. I'm checking how it is going.

<Transverse mode spurious generation conditions>
Next, the conditions under which the superiority of this configuration is expressed will be examined.

FIG. 6 shows a phase characteristic when the thickness of the piezoelectric layer 2 is 1λ or more as Comparative Example 3. The SAW element of Comparative Example 3 is different from that of Example 1 in that the pitch of the electrode fingers 32 is 1.1 μm and the thickness of the piezoelectric layer is 18 p (that is, 9λ). While the duty in the intersection area is 0.53, the duty in the dummy area is 0.53 to 0.70 (0.53, 0.57, 0.61, 0.66, 0.70). ). These will be referred to as Comparative Examples 3-1 to 3-5 in order.

FIG. 6 shows the phase characteristics of the SAW element of Comparative Example 3 as described above, which corresponds to FIGS. 3(a) and 3(b). In FIG. 6, the characteristics of Comparative Examples 3-1 to 3-4 are sequentially shown by a solid line, a dotted line, a broken line, a one-dot chain line, and a long two-dot chain line, respectively. As is clear from FIG. 6, when the piezoelectric layer 2 has a thickness of 1λ or more, bulk wave spurs are occasionally seen, but no transverse mode ripple near the resonance frequency and the anti-resonance frequency is confirmed, and the dummy electrode No characteristic change due to the duty of the area was also confirmed.

From this, it is assumed that the characteristic change due to the duty of the dummy electrode region appears after the thickness of the piezoelectric layer 3 becomes less than 1λ and the SAW is confined in the piezoelectric layer.

Next, FIG. 7 shows the phase characteristics of the SAW element of Comparative Example 4. The SAW element of Comparative Example 4 was the same as that of Example 1 except that the inclination angle was 0°, the pitch of the electrode fingers 32 was 1.1 μm, and the thickness of the piezoelectric layer was 0.7λ. different. The duty in the intersecting region is 0.53, whereas the duty in the dummy electrode region is 0.70 (Comparative Example 4-1) and the same as the intersecting region (Comparative Example 4-). Two conditions, 2) and 2) were set.

FIG. 7 shows the phase characteristics of the SAW element of Comparative Example 4 and corresponds to FIGS. 3(a) and 3(b). In FIG. 7, the characteristic of Comparative Example 4-1 is shown by a solid line, and the characteristic of Comparative Example 4-2 is shown by a broken line. As is clear from FIG. 7, when the tilt angle is 0°, the transverse mode ripple near the resonance frequency and the anti-resonance frequency is large, and no characteristic change due to the duty of the dummy region was confirmed.

From this, it is estimated that the characteristic change due to the duty of the dummy region is not exhibited until the IDT electrode is tilted.

From the above, the characteristic change due to the duty of the dummy region is not achieved until the thickness of the piezoelectric layer becomes less than 1λ, the SAW is confined in the piezoelectric layer, and the transverse mode ripple is reduced by tilting the IDT electrode. It was confirmed that this is a phenomenon that produces an effect.

<Modification>
Next, the tip shape of the electrode finger 32 will be examined. As Comparative Example 5, phase characteristics were measured for a SAW element having a configuration in which the electrode finger 32 and the dummy electrode 35 have a widened portion at the tips thereof.
The widened portion can also be referred to as a protruding portion that extends in the SAW propagation direction or in the region between the electrode fingers 32 or between the dummy electrode 35 and the electrode finger 32.

FIG. 8 shows an enlarged view of the low frequency side of the resonance frequency (the region surrounded by the broken line in FIG. 3A) in the phase characteristics of Comparative Example 5 and Example 1. In FIG. 8, the solid line shows the characteristics of Example 1 and the broken line shows the characteristics of Comparative Example 5. As is clear from FIG. 8, it was confirmed that the phase characteristic on the low frequency side of the resonance frequency deteriorates when the widened portion is provided. From the above, the IDT electrode 3 may have a shape having no widened portion near the tip of the electrode finger 32.

Further, the widened portion may cause electrostatic breakdown. For this reason, as shown in FIG. 9, the dummy region has a uniform line width, and the width gradually decreases from that to the intersecting region to form a protrusion that projects in the SAW propagation direction. The configuration may not be provided.

<Modification 2>
Next, in the case of thickening the root of the electrode finger 32, a case was examined in which the length from the root was made different. As a result, the resonance frequency and the anti-resonance frequency are larger in the case of thickening up to the position of the virtual line connecting the tips of the other electrode fingers than in the case of thickening up to the virtual line (L1, L2) connecting the tips of the dummy electrodes. It was found that the maximum phase value between and can be increased.

Specifically, the maximum phase was 88.67 deg when thickened from the root to the virtual line (L1, L2) connecting the tips of the dummy electrodes, while the virtual line connecting the tips of the other electrode fingers. The maximum phase was 88.74 deg when thickened to the position.

No particular difference was confirmed in the characteristics other than the maximum phase. That is, spurious and the like did not occur even when the length from the root was made different.

In the above example, the case where the intermediate layer 7 is interposed between the piezoelectric layer 3 and the supporting substrate 5 has been described as an example, but the present invention is not limited to this. For example, only the piezoelectric layer 3 may be used, the piezoelectric layer 3 and the support substrate 5 may be directly bonded, or two or more intermediate layers 7 may be laminated. In that case, a layer made of a material having a higher acoustic velocity than the piezoelectric layer 3 may be included. Further, between the piezoelectric layer 3 and the supporting substrate 7, a multilayer film reflector in which low acoustic velocity films and high acoustic velocity films are alternately and repeatedly arranged may be located.

Further, in the above-mentioned example, the direction in which the tips of the first electrode fingers are connected together with the direction in which the tips of the second electrode fingers are connected is also inclined with respect to the SAW propagation direction, but either one of them may have an effect. Further, in the above-described example, the configuration is such that the entire IDT electrode is uniformly inclined, but only a part of the IDT electrode may be inclined, or the inclination angle may not be uniform.

Further, in the above-mentioned example, the case where both the widths of the first dummy electrode and the second dummy electrode are made large has been described, but either one may be used.

In the above example, the case of the one-port resonator has been described as an example, but it is not limited to this. For example, the present invention is also applicable to comb-teeth electrodes that form a longitudinally coupled resonator filter such as DMS.

Further, a filter and a duplexer (a duplexer, a multiplexer, etc.) including a plurality of the SAW elements 1 described above may be used. For example, a plurality of SAW elements 1 may be connected in a ladder type to form a filter.

Further, the communication device may be configured by combining the filter, the duplexer, or the like configured as described above and the IC.

1: acoustic wave element (SAW element), 2: piezoelectric substrate, 2A: upper surface, 3: excitation electrode (IDT electrode), 30: comb-teeth electrode, 31: bus bar (first bus bar 31a, second bus bar 31b), 32 : Electrode finger, 35: dummy electrode (first dummy electrode 35a, second dummy electrode 35b), 4: reflector electrode

Claims (9)

A piezoelectric film,
An IDT electrode located on the piezoelectric film,
The IDT electrode is
A first bus bar and a second bus bar, which are spaced apart,
A plurality of first electrode fingers connected to the first bus bar,
A plurality of second electrode fingers connected to the second bus bar and interleaved with the first electrode fingers in an alternating manner;
A first dummy electrode which is connected to the first bus bar and faces the tip of the second electrode finger with a space between them;
A second dummy electrode that is connected to the second bus bar and faces the tip of the first electrode finger with a gap between them;
Have
A direction connecting the tips of the first electrode fingers and an arrangement direction of the first electrode fingers and the second electrode fingers form an inclination angle,
The width of the second dummy electrode in the arrangement direction is thicker than the width of the first electrode finger in the intersecting region where the first electrode finger and the second electrode finger intersect,
The piezoelectric film is less than 1λ, where λ is a wavelength determined by the period of the first electrode fingers and the second electrode fingers.
Acoustic wave device. The width of the second electrode finger is thicker in the second dummy electrode region, which is closer to the second bus bar than the imaginary line connecting the tips of the second dummy electrodes, compared to the intersecting region. 1. The elastic wave device according to 1. The acoustic wave device according to claim 2, wherein the duty in the second dummy electrode region is larger than the duty in the intersecting region by 0.08 or more. The acoustic wave device according to claim 3, wherein the duty in the second dummy electrode region is larger than the duty in the intersecting region in the range of 0.08 to 0.16. The acoustic wave device according to claim 1, wherein the tips of the first electrode finger and the second electrode finger do not include a widened portion. A support substrate, which is located on the opposite side of the piezoelectric film from the side where the IDT electrode is located, and has a higher acoustic velocity than the acoustic velocity of elastic waves in the piezoelectric film, is provided between the piezoelectric film and the supporting substrate. The acoustic wave device according to claim 1, wherein an intermediate layer made of a material having a lower acoustic velocity than the piezoelectric film is located. 7. The acoustic wave device according to claim 6, wherein the second electrode finger has a larger width in a region closer to the second bus bar than an imaginary line connecting the tips of the first electrode fingers as compared with the intersecting region. .. The support substrate is located on the opposite side of the piezoelectric film from the side where the IDT electrode is located, and a multilayer film reflector is located between the piezoelectric film and the support substrate. The elastic wave device as described in 1. A direction connecting the tips of the second electrode fingers and the arrangement direction form an inclination angle,
The acoustic wave device according to claim 1, wherein a width of the first dummy electrode in the arrangement direction is thicker than a width of the second electrode finger in the intersecting region.