Elastic wave device and communication apparatus

Abstract

To improve the frequency characteristics of an elastic wave device.SOLUTION: A first electrode finger includes a slender portion located at the tip of the first electrode finger and a non-slender portion located closer to the base of the first electrode finger than the slender portion. A dielectric layer includes a first region that overlaps at least part of the slender portion in a planar view, and does not overlap at least part of the non-slender portion in a planar view.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to acoustic wave devices and communication apparatus. [Background technology]

[0002] Patent Document 1 discloses a configuration in which a mass-adding film is provided on a first electrode finger and a second electrode finger of an IDT electrode. IDT is an abbreviation for interdigital transducer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-92095 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is expected that the frequency characteristics of acoustic wave devices can be improved by reducing the energy loss near the resonant frequency. [Means for solving the problem]

[0005] An acoustic wave device according to one embodiment of the present disclosure has a piezoelectric body, a first electrode finger, a second electrode finger adjacent to the first electrode finger, and a bus bar electrically connected to the second electrode finger, and comprises an IDT electrode located above the piezoelectric body, and a dielectric layer located above the IDT electrode, wherein the thickness of the piezoelectric body is less than twice the pitch of the first electrode finger and the second electrode finger, the first electrode finger includes a slender portion located at the tip of the first electrode finger and a non-fine portion located closer to the base of the first electrode finger than the slender portion, and the dielectric layer includes a first region that overlaps with at least a portion of the slender portion in a planar view and does not overlap with at least a portion of the non-fine portion in the planar view. Effect of the Invention

[0006] According to one aspect of the present disclosure, it is possible to improve the frequency characteristics of an acoustic wave device. [Brief description of the drawings]

[0007] [Figure 1] 1 is a plan view illustrating a schematic configuration of an acoustic wave device according to a first embodiment of the present disclosure. [Diagram 2] 1 is a cross-sectional view along the line AA illustrating a schematic configuration of an acoustic wave device according to a first embodiment of the present disclosure. [Diagram 3] FIG. 11 is a plan view illustrating a schematic configuration of a modified example of the acoustic wave device according to the first embodiment of the present disclosure. [Figure 4] 1 is a table showing initial simulation conditions in the LT model. [Diagram 5] 1 is a table showing initial simulation conditions in an LN model. [Figure 6] 1 is a table showing a list of dielectric layer configurations applied to the 101 model. [Figure 7] This is a table listing the conditions under which good frequency characteristics were obtained in the LT model. [Figure 8] 1 is a table listing the conditions under which good frequency characteristics were obtained in the LN model. [Figure 9] 11A and 11B are diagrams illustrating an improvement in frequency characteristics of an acoustic wave device according to a comparative example, achieved by providing a dielectric layer. [Figure 10] 11A and 11B are diagrams illustrating an improvement in frequency characteristics of an acoustic wave device according to a comparative example, achieved by providing a dielectric layer. [Figure 11] 11A and 11B are diagrams illustrating an improvement in frequency characteristics of an acoustic wave device according to a comparative example, achieved by providing a dielectric layer. [Figure 12] 10 is a graph showing frequency characteristics with respect to a difference between a fill factor of the first electrode fingers and the second electrode fingers in an inner region and a fill factor of the first electrode fingers and the second electrode fingers in an edge region. [Figure 13]10 is a graph illustrating the change in sound velocity in the edge region and the inner region with respect to the thickness of the dielectric layer in the 101 model. [Figure 14] 10 is a graph illustrating the change in sound velocity in the edge region and the inner region with respect to the thickness of the dielectric layer in the 101 model. [Figure 15] 10 is a graph illustrating the change in sound velocity in the edge region and the inner region with respect to the thickness of the dielectric layer in the 101 model. [Figure 16] 10 is a graph illustrating the change in sound velocity in the edge region and the inner region with respect to the thickness of the dielectric layer in the 101 model. [Figure 17] 10 is a graph illustrating the change in sound velocity in the edge region and the inner region with respect to the thickness of the dielectric layer in the 101 model. [Figure 18] 13 is a graph showing excellent frequency characteristics in the LT model. [Figure 19] 13 is a graph showing excellent frequency characteristics in the LT model. [Figure 20] 1 is a graph showing good frequency characteristics in an LN model. [Figure 21] 1 is a graph showing good frequency characteristics in an LN model. [Figure 22] 13 is a graph showing the frequency characteristics of the LT model. [Figure 23] 13 is a graph showing the frequency characteristics of the LT model. [Figure 24] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 25] 13 is a graph showing the frequency characteristics of the LT model. [Figure 26] 13 is a graph showing the frequency characteristics of the LT model. [Figure 27] 13 is a graph showing the frequency characteristics of the LT model. [Figure 28] 13 is a graph showing the frequency characteristics of the LT model. [Figure 29] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 30]13 is a graph showing the frequency characteristics of the LT model. [Diagram 31] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 32] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 33] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 34] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 35] 13 is a graph showing the frequency characteristics of the LT model. [Diagram 36] 13 is a graph showing the frequency characteristics of the LT model. [Figure 37] 13 is a graph showing the frequency characteristics of the LT model. [Figure 38] 13 is a graph showing the frequency characteristics of an LN model. [Figure 39] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 40] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 41] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 42] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 43] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 44] 13 is a graph showing the frequency characteristics of an LN model. [Diagram 45] 13 is a graph showing the frequency characteristics of an LN model. [Figure 46] FIG. 11 is a cross-sectional view illustrating a schematic configuration of an acoustic wave device according to a second embodiment of the present disclosure. [Figure 47] FIG. 11 is a schematic diagram of a communication device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present disclosure. For convenience of explanation, the same reference numerals are given to components having the same functions as those described above, and the description thereof may not be repeated.

[0009] [Embodiment 1] Fig. 1 is a plan view showing a schematic configuration of an acoustic wave device 101 according to a first embodiment of the present disclosure, and Fig. 2 is a cross-sectional view taken along line AA showing a schematic configuration of the acoustic wave device 101 according to the first embodiment of the present disclosure.

[0010] The acoustic wave device 101 includes a piezoelectric body 1, an IDT electrode 2, a dielectric layer 3, multiple multilayer reflective films 4, and a support substrate 5. The support substrate 5, multiple multilayer reflective films 4, piezoelectric body 1, IDT electrode 2, and dielectric layer 3 are laminated in this order. Each of the multiple multilayer reflective films 4 includes, in order from the piezoelectric body 1 side, a low acoustic impedance layer 6 and a high acoustic impedance layer 7. As an example, the number of multilayer reflective films 4 in the acoustic wave device 101 is four.

[0011] The piezoelectric body 1 may include at least one of LiTaO3 and LiNbO3. LiTaO3 may be referred to as lithium tantalate and may be written as LT. LiNbO3 may be referred to as lithium niobate and may be written as LN. The thickness of the piezoelectric body 1 is T1.

[0012] The IDT electrode 2 is located in a layer above the piezoelectric body 1. The IDT electrode 2 has first electrode fingers 8, second electrode fingers 9, and a bus bar 10. The second electrode fingers 9 are adjacent to the first electrode fingers 8. The bus bar 10 is electrically connected to the second electrode fingers 9. Although not shown, the IDT electrode 2 further has a bus bar electrically connected to the first electrode fingers 8.

[0013] 1 and 2 show directions D1, D2, and D3 that are perpendicular to each other. The D1 direction can be defined as the arrangement direction of the first electrode fingers 8 and the second electrode fingers 9. The D3 direction can be defined as the thickness direction of the piezoelectric body 1. The longitudinal direction of the first electrode fingers 8 and the longitudinal direction of the second electrode fingers 9 are approximately parallel to the D2 direction.

[0014] The dielectric layer 3 is located above the IDT electrode 2. The dielectric layer 3 includes a first region 12 that overlaps at least a part of a slender portion 19 of the first electrode finger 8, which will be described later, in a plan view of the acoustic wave device 101. Hereinafter, the plan view of the acoustic wave device may be simply referred to as a plan view. In the plan view, the first region 12 of the dielectric layer 3 and the tip portion 11 of the first electrode finger 8 overlap each other. The thickness of the dielectric layer 3 is T3. A region that includes the tip portion 11 of the first electrode finger 8 and a part of the second electrode finger 9 facing the tip portion 11 of the first electrode finger 8 and extends in the D1 direction is referred to as an edge region 22. A region located inside the intersection region of the first electrode finger 8 and the second electrode finger 9 from the edge region 22 is referred to as an inner region 23. The first region 12 overlaps the edge region 22.

[0015] In a plan view, dielectric layer 3 may include a second region 14 overlapping with gap 13 between first electrode finger 8 and bus bar 10, and a third region 15 overlapping with bus bar 10. In a plan view, second region 14 of dielectric layer 3 and gap 13 between first electrode finger 8 and bus bar 10 may overlap with each other. In a plan view, third region 15 of dielectric layer 3 and bus bar 10 may overlap with each other.

[0016] The dielectric layer 3 may include at least one of a high acoustic velocity dielectric material and Ta2O5. The high acoustic velocity dielectric material may be defined as a material in which the acoustic velocity in the high acoustic velocity dielectric material is higher than that in the piezoelectric body 1. The high acoustic velocity dielectric material may be any of SiO2, AlN, SiN, Al2O3, and TiO2. The use of a high acoustic velocity dielectric material can reduce the decrease in the rate of change of the acoustic velocity in the edge region 22 relative to the acoustic velocity in the inner region 23 described below, caused by the dielectric layer 3. This is because the duty change of the slender portion 19 can be reduced.

[0017] The thickness T3 of the dielectric layer 3 may be 0.015 times or more and 0.1 times or less than the thickness T1 of the piezoelectric body 1. A frequency band around the resonant frequency is defined as a first frequency band, a frequency band around the anti-resonant frequency is defined as a third frequency band, and a frequency band between the first and third frequency bands is defined as a second frequency band. If the thickness T3 is less than 0.015 times the thickness T1, there is a risk of energy loss becoming large in the second frequency band. If the thickness T3 is more than 0.1 times the thickness T1, there is a risk of energy loss becoming large in the first frequency band.

[0018] The multilayer reflective film 4, i.e., the low acoustic impedance layer 6 and the high acoustic impedance layer 7, are located below the piezoelectric body 1. The acoustic impedance of the low acoustic impedance layer 6 is lower than the acoustic impedance of the high acoustic impedance layer 7. The low acoustic impedance layer 6 may contain SiO2. The high acoustic impedance layer 7 may contain at least one of HfO2, Ta2O5, and ZrO2.

[0019] The supporting substrate 5 supports the piezoelectric body 1, the IDT electrode 2, the dielectric layer 3, and the multiple multilayer reflective films 4. The supporting substrate 5 may be a Si substrate.

[0020] The acoustic wave device 101 may excite an antisymmetric A1 mode. The acoustic wave device 101 may excite a bulk wave. The vibration mode of the acoustic wave device 101 that excites a bulk wave may be a thickness shear mode. The acoustic wave device 101 that excites a bulk wave may not include the multilayer reflective film 4.

[0021] Pitch p of first electrode finger 8 and second electrode finger 9 is defined as the distance between center 16 of first electrode finger 8 and center 17 of second electrode finger 9 in direction D1. The pitch means the center-to-center distance, and can also be said to mean the repetition interval. Thickness T1 of piezoelectric body 1 is equal to or less than twice pitch p of first electrode finger 8 and second electrode finger 9. This makes it possible to configure acoustic wave device 101 that matches the wavelength of acoustic waves propagating within piezoelectric body 1.

[0022] First electrode finger 8 includes non-detailed portion 18. In first electrode finger 8, non-detailed portion 18 is located closer to the base than tip portion 11. Non-detailed portion 18 may be a portion of first electrode finger 8 having a width that matches the wavelength of an elastic wave propagating through piezoelectric body 1. Non-detailed portion 18 may be included in a central portion of first electrode finger 8 in the longitudinal direction of first electrode finger 8.

[0023] The dielectric layer 3 does not overlap at least a portion of the non-detailed portion 18 in a plan view. The tip portion 11 includes a slender portion 19 that is narrower than the non-detailed portion 18. The width W19 of the slender portion 19 is smaller than the width W18 of the non-detailed portion 18. The slender portion 19 may be the entire tip portion 11 or may be a portion of the tip portion 11. The dielectric layer 3 may overlap a portion of the non-detailed portion 18.

[0024] Acoustic wave device 101 can be interpreted as having the following configuration. First electrode finger 8 includes a slender portion 19 located at tip portion 11 of first electrode finger 8, and a non-fine portion 18 located closer to the base of first electrode finger 8 than slender portion 19. Dielectric layer 3 includes a first region 12 that overlaps at least a portion of slender portion 19 in a plan view, and does not overlap at least a portion of non-fine portion 18 in a plan view.

[0025] When width W18 is non-uniform with respect to the position within non-fine portion 18 in the longitudinal direction of first electrode finger 8, width W18 may be any of the maximum value, minimum value, average value, median value, and median value of the width within entire non-fine portion 18. When width W19 is non-uniform with respect to the position within thin portion 19 in the longitudinal direction of first electrode finger 8, width W19 may be any of the maximum value, minimum value, average value, median value, and median value of the width within entire thin portion 19. The maximum value, minimum value, average value, median value, and median value selected may be mutually consistent for width W18 and width W19.

[0026] The length L11 of the tip 11 of the first electrode finger 8 in the longitudinal direction may be equal to or greater than the thickness T1 of the piezoelectric body 1 and may be equal to or less than five times the thickness T1 of the piezoelectric body 1. If the length L11 is less than the thickness T1, the area where the dielectric layer 3 and the first electrode finger 8 overlap in a plan view is too small, and the benefit of the dielectric layer 3 is small. If the length L11 is more than five times the thickness T1, the volume of the dielectric layer 3 is too large, and there is a risk of large energy loss in the second frequency band.

[0027] An area including slender portion 19 and extending in the arrangement direction of first electrode fingers 8 is defined as edge region 22, and an area including non-fine portions 18 and located inside edge region 22 among the intersection regions of first electrode fingers 8 and second electrode fingers 9 is defined as inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 may be 0.03 or more and 0.3 or less. The duty of first electrode finger 8 and second electrode finger 9 is defined as the ratio of the sum of the width of first electrode finger 8 and the width of second electrode finger 9 to twice the pitch p.

[0028] The IDT electrode 2 may have a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. The dummy electrode 20 may have a function of more precisely controlling the frequency characteristics of the acoustic wave device 101. In Fig. 1, the dummy electrode 20 is a finger-like dummy electrode that extends in a finger-like manner from the bus bar 10 in the longitudinal direction of the second electrode finger 9.

[0029] Fig. 3 is a plan view showing a schematic configuration of a modified example of the acoustic wave device 101 according to the first embodiment of the present disclosure. In Fig. 3, the dummy electrode 20 is a planar dummy electrode extending in a plane defined by the D1 direction from the bus bar 10 and the longitudinal direction of the second electrode fingers 9. Note that Figs. 1 to 3 are schematic views of a cut-out portion of the acoustic wave element, and in reality, a total of 50 to several hundreds of first electrode fingers 8 and second electrode fingers 9 of the IDT electrode 2 are periodically arranged in the D1 direction. Also, only the right half of the acoustic wave element is shown in the D2 direction, and the left half of the acoustic wave element is symmetrically arranged in the D2 positive direction.

[0030] A simulation model of an acoustic wave device 101 in which the material of the piezoelectric body 1 is LT, and a simulation model of an acoustic wave device 101 in which the material of the piezoelectric body 1 is LN are used. The simulation model of the acoustic wave device 101 is also referred to as the 101 model. The 101 model in which the material of the piezoelectric body 1 is LT is also referred to as the LT model. The 101 model in which the material of the piezoelectric body 1 is LN is also referred to as the LN model. These models are examples of parameters that efficiently excite an A1 mode SAW (Surface Acoustic Wave) resonator. However, the effects of the present disclosure are not limited to these parameters, and each parameter can be optimized as appropriate to have characteristics suited to the purpose.

[0031] Fig. 4 is a table showing the initial simulation conditions in the LT model. Unless otherwise specified, the LT model is assumed to have a configuration according to the initial simulation conditions in the LT model. Fig. 5 is a table showing the initial simulation conditions in the LN model. Unless otherwise specified, the LN model is assumed to have a configuration according to the initial simulation conditions in the LN model.

[0032] The LT layer in FIG. 4 and the LN layer in FIG. 5 show the Euler angles of the piezoelectric body 1 in units of degrees. Si substrate: The Euler angles of the support substrate 5 made of Si are shown in units of degrees. Pitch(um): Pitch p is expressed in units of μm. Dummy length (um): The length of the dummy electrode 20 is shown in the unit μm. Gap (um): The length of the gap 13 between the first electrode finger 8 and the dummy electrode 20 in the longitudinal direction of the first electrode finger 8, expressed in μm. Intersection width (um): The intersection width of the first electrode finger 8 and the second electrode finger 9 in the 101 model is shown in μm. Piezoelectric film thickness (um): Thickness T1 is shown in units of μm SiO2 thickness (um): The thickness of the low acoustic impedance layer 6 is shown in μm. HfO2 thickness (um): The thickness of the high acoustic impedance layer 7 is shown in μm. Electrode thickness (um): The thickness of the IDT electrode 2 is shown in μm. The definitions in the tables shown in Fig. 4 and Fig. 5 are as described above. In the simulation, the periodic boundary condition was used in the D1 direction (propagation direction of elastic waves).

[0033] FIG. 6 is a table showing a list of the configurations of the dielectric layer 3 applied to the 101 model.

[0034] Z: indicates acoustic impedance VL: Indicates the speed of sound The definitions in the table shown in FIG. 6 are as described above.

[0035] For the 101 model, a length of 1 μm is applied as the length of tip portion 11 and first region 12 in the longitudinal direction of first electrode finger 8.

[0036] Fig. 7 is a table listing conditions under which good frequency characteristics were obtained in the LT model, and Fig. 8 is a table listing conditions under which good frequency characteristics were obtained in the LN model.

[0037] Additional film material: indicates the material of the dielectric layer 3 Added film thickness (um): Thickness T3 is shown in μm. Additional film thickness (xt): Shown as a ratio of thickness T3 to thickness T1 Dummy electrode: The presence or absence of a dummy electrode 20. "With dummy" indicates that a finger-shaped dummy electrode is present, and "Dummy solid" indicates that a planar dummy electrode is present. The additional film position: "dummy portion + IDT end" indicates that, in plan view, the dielectric layer 3 overlaps the tip portion 11 and the gap 13, and also overlaps the dummy electrode 20 when the dummy electrode 20 is located in the gap 13. Duty change at the IDT end: The decimal following “Duty-” is the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 Around the resonance point: Shows the evaluation of the frequency characteristics of the first frequency band Resonance point to anti-resonance point: Shows the evaluation of the frequency characteristics of the second frequency band Around the anti-resonance point: Shows the evaluation of the frequency characteristics of the third frequency band The definitions in the tables shown in Fig. 7 and Fig. 8 are as described above. Common to the area around the resonance point, the area between the resonance point and the anti-resonance point, and the area around the anti-resonance point, the evaluation is performed on a two-level scale: "○" indicating that the improvement effect of the frequency characteristics is significant, and "△" indicating that the improvement effect of the frequency characteristics is not significant but is somewhat significant.

[0038] 7 and 8, it can be seen that the frequency characteristics are improved in all of the first, second, and third frequency bands under the following conditions (1) to (8). Regarding the ratio of the thickness T3 of the dielectric layer 3 to the thickness T1 of the piezoelectric body 1, a numerical range is set that takes into consideration an error of -15% or more and 15% or less that may occur based on the current technical level with respect to the numerical values ​​shown in Figs. 7 and 8. Regarding the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22, a numerical range is set that takes into consideration an error of -25% or more and 25% or less that may occur based on the current technical level with respect to the numerical values ​​shown in Figs. 7 and 8.

[0039] (1) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is AlN. The thickness T3 of the dielectric layer 3 is 0.075×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.075×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the gap 13 between the first electrode finger 8 and the bus bar 10. The region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as the edge region 22, and the region including the non-detailed portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as the inner region 23. In this case, the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.18×0.75 or more and 0.18×1.25 or less.

[0040] (2) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is AlN. The thickness T3 of the dielectric layer 3 is 0.075×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.075×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the first electrode finger 8 and the gap 13 of the bus bar 10. The IDT electrode 2 does not have a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. A region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as an edge region 22, and a region including the non-detailed portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is 0.27×0.75 or more and 0.27×1.25 or less.

[0041] (3) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is SiO2. The thickness T3 of the dielectric layer 3 is 0.075×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.075×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the gap 13 between the first electrode finger 8 and the bus bar 10. The IDT electrode 2 has a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. A region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as an edge region 22, and a region including the non-detailed portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as an inner region 23. In this case, the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is not less than 0.18×0.75 and not more than 0.18×1.25. When the dummy electrode 20 is a planar dummy electrode, the effect of improving the frequency characteristics in the first frequency band is remarkable.

[0042] (4) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is Ta2O5. The thickness T3 of the dielectric layer 3 is 0.025×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.025×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps with the first electrode fingers 8 and the gaps 13 of the busbar 10. A region including the slender portions 19 and extending in the arrangement direction of the first electrode fingers 8 is defined as an edge region 22, and a region including the non-fine portions 18 and located inside the edge region 22 among the intersection regions of the first electrode fingers 8 and the second electrode fingers 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is not less than 0.18×0.75 and not more than 0.18×1.25. When IDT electrode 2 has a planar dummy electrode located in gap 13 and overlapping dielectric layer 3 in a planar view, the improvement in frequency characteristics in all of the first, second, and third frequency bands is remarkable.

[0043] (5) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is Ta2O5. The thickness T3 of the dielectric layer 3 is 0.025×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.025×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the first electrode finger 8 and the gap 13 of the bus bar 10. The IDT electrode 2 does not have a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. A region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as an edge region 22, and a region including the non-detailed portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is 0.27×0.75 or more and 0.27×1.25 or less.

[0044] (6) The material of the piezoelectric body 1 is LiNbO3. The material of the dielectric layer 3 is SiO2. The thickness T3 of the dielectric layer 3 is 0.080×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.080×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the first electrode finger 8 and the gap 13 of the bus bar 10. The IDT electrode 2 does not have a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. A region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as an edge region 22, and a region including the non-fine portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is 0.1×0.75 or more and 0.1×1.25 or less.

[0045] (7) The material of the piezoelectric body 1 is LiNbO3. The material of the dielectric layer 3 is Ta2O5. The thickness T3 of the dielectric layer 3 is 0.027×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.027×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps with the first electrode fingers 8 and the gaps 13 of the busbar 10. A region including the slender portions 19 and extending in the arrangement direction of the first electrode fingers 8 is defined as an edge region 22, and a region including the non-fine portions 18 and located inside the edge region 22 among the intersection regions of the first electrode fingers 8 and the second electrode fingers 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is 0.1×0.75 or more and 0.1×1.25 or less.

[0046] (8) The material of the piezoelectric body 1 is LiNbO3. The material of the dielectric layer 3 is Ta2O5. The thickness T3 of the dielectric layer 3 is 0.020×0.85 times or more the thickness T1 of the piezoelectric body 1 and 0.020×1.15 times or less the thickness T1 of the piezoelectric body 1. In a plan view, the dielectric layer 3 overlaps the first electrode finger 8 and the gap 13 of the bus bar 10. The IDT electrode 2 does not have a dummy electrode 20 located in the gap 13 and overlapping with the dielectric layer 3 in a plan view. A region including the slender portion 19 and extending in the arrangement direction of the first electrode finger 8 is defined as an edge region 22, and a region including the non-detailed portion 18 and located inside the edge region 22 among the intersection regions of the first electrode finger 8 and the second electrode finger 9 is defined as an inner region 23. In this case, the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is 0.06×0.75 or more and 0.06×1.25 or less.

[0047] 9 to 11 are diagrams illustrating the effect of improving the frequency characteristics of an acoustic wave device 102 according to a comparative example by providing a dielectric layer 3. A simulation model of the acoustic wave device 102 is used. The simulation model of the acoustic wave device 102 is also referred to as the 102 model.

[0048] 9 is a plan view showing a schematic configuration of acoustic wave device 102. Acoustic wave device 102 has the same configuration as acoustic wave device 101, except that tip portion 11 does not include thin portion 19 and first electrode finger 8 and second electrode finger 9 have constant widths.

[0049] 10 and 11 are graphs showing frequency characteristics versus thickness T3 in the 102 model.

[0050] frequency(MHz):Frequency is expressed in units of MHz Phase (deg): The phase of the impedance of the corresponding 101 model and 102 model is shown in degrees. REF: shows the characteristics of a simulation model of an acoustic wave device 102 with the dielectric layer 3 omitted. 501: Shows the characteristics of the 102 model where thickness T3 is 0.013 times thickness T1 502: Shows the characteristics of the 102 model where thickness T3 is 0.025 times thickness T1 503: Shows the characteristics of the 102 model where thickness T3 is 0.075 times thickness T1 504: Shows the characteristics of the 102 model where thickness T3 is 0.125 times thickness T1 The definitions of the graphs shown in Fig. 10 and Fig. 11 are as described above. The phase of the impedance is related to the loss of the acoustic wave device. On the lower frequency side than the resonant frequency and on the higher frequency side than the anti-resonant frequency, the closer the phase is to -90°, the smaller the loss. In addition, between the resonant frequency and the anti-resonant frequency, the closer the phase is to +90°, the smaller the loss.

[0051] 10 and 11, frequency characteristics are shown under the assumption that the material of the piezoelectric body 1 is LT and the material of the dielectric layer 3 is SiO2 in 501 to 504. In addition, conditions not described above are also the same in 501 to 504.

[0052] 10, it can be seen that the greater the thickness T3, the greater the disturbance in the phase of the impedance with respect to frequency in the first frequency band, and the worse the frequency characteristics tend to be. This is thought to be because the greater the thickness T3, the slower the sound speed in the edge region 22 becomes, causing ripples in the frequency characteristics in the first frequency band.

[0053] According to FIG. 11, it can be seen that as the thickness T3 increases, in the second frequency band, the disturbance in the phase of the impedance with respect to the frequency decreases, and the frequency characteristics tend to improve.

[0054] FIG. 12 is a graph showing frequency characteristics versus the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22. As shown in FIG.

[0055] Shows the characteristics of the 505:102 model 506: This shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.18. The definitions of the graph shown in Fig. 12 are as described above. For the sake of convenience, the explanation of the same definitions as those explained above will be omitted.

[0056] 12, frequency characteristics are shown under the same conditions as in 505 and 506, that the material of the piezoelectric body 1 is LT, the IDT electrode 2 has a planar dummy electrode, the material of the dielectric layer 3 is SiO2, and the thickness T3 is 0.03 μm, which is 0.075 times the thickness T1. Conditions not described above are also the same in 505 and 506.

[0057] According to Figure 12, by setting the difference between the duty cycle of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty cycle of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 to 0.18, it can be seen that in the first frequency band, the phase disturbance of the impedance with respect to frequency is reduced, and the frequency characteristics tend to improve.

[0058] Each of Figs. 13 to 17 is a graph illustrating the change in sound velocity in the edge region 22 and the inner region 23 with respect to the thickness T3 in the 101 model.

[0059] Additional film thickness (xt): Shows the ratio of thickness T3 to thickness T1 dfr: (sound velocity in edge region 22 / sound velocity in inner region 23) - 1 is converted to a percentage, and indicates the rate of change in the sound velocity in edge region 22 relative to the sound velocity in inner region 23. The sound velocity in edge region 22 is in a state where first region 12 and thin portion 19 of dielectric layer 3 overlap in plan view. 507: Shows the characteristics of the 102 model as a reference 508: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.09 509: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.18. 510: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.27. 511: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.05. 512: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.1 513: shows the characteristics of the 101 model in which the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is 0.15. Figures 13 to 15 show the characteristics of the LT model, and Figures 16 and 17 show the characteristics of the LN model. The material of the dielectric layer 3 is AlN in Figure 13, SiO2 in Figures 14 and 16, and Ta2O5 in Figures 15 and 17.

[0060] 13 to 17, regions where the frequency characteristics are deemed to be good are enclosed by rectangles. A region including slender portion 19 and extending in the arrangement direction of first electrode fingers 8 is defined as edge region 22, and a region including non-fine portions 18 and located inside edge region 22 among the intersection regions of first electrode fingers 8 and second electrode fingers 9 is defined as inner region 23. In this case, the absolute value of the rate of change of the sound velocity in edge region 22 relative to the sound velocity in inner region 23 may be 1% or less. According to FIGS. 13 to 17, the absolute value is 1% or less under the following conditions (A) to (E), and therefore it can be seen that there is an effect of improving the frequency characteristics. Furthermore, the rate of change may be 0% or more and 1% or less.

[0061] (A) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is AlN. The ratio of the thickness T3 of the dielectric layer 3 to the thickness T1 of the piezoelectric body 1 is defined as d, and the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is defined as q. In this case, 0.05≦d≦0.1 and 3.387d-0.106≧q≧3.300d+0.133 are satisfied.

[0062] (B) The material of the piezoelectric body 1 is LiTaO3. The material of the dielectric layer 3 is SiO2. The ratio of the thickness T3 of the dielectric layer 3 to the thickness T1 of the piezoelectric body 1 is defined as d, and the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is defined as q. In this case, 0.05≦d≦0.1 and 3.113d-0.124≧q≧2.814d+0.142 are satisfied.

[0063] (C) The material of piezoelectric body 1 is LiTaO3. The material of dielectric layer 3 is Ta2O5. The ratio of thickness T3 of dielectric layer 3 to thickness T1 of piezoelectric body 1 is defined as d, and the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is defined as q. In this case, 0.0125≦d≦0.035 and 10.694d-0.135≧q≧10.196d+0.131 are satisfied.

[0064] (D) The material of piezoelectric body 1 is LiNbO3. The material of dielectric layer 3 is SiO2. The ratio of thickness T3 of dielectric layer 3 to thickness T1 of piezoelectric body 1 is defined as d, and the difference between the duty of first electrode finger 8 and second electrode finger 9 in inner region 23 and the duty of first electrode finger 8 and second electrode finger 9 in edge region 22 is defined as q. In this case, 0.05≦d≦0.1 and 1.312d-0.028≧q≧0.790d+0.113 are satisfied.

[0065] (E) The material of the piezoelectric body 1 is LiNbO3. The material of the dielectric layer 3 is Ta2O5. The ratio of the thickness T3 of the dielectric layer 3 to the thickness T1 of the piezoelectric body 1 is defined as d, and the difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is defined as q. In this case, 0.01≦d≦0.035 and 5.566d-0.050≧q≧3.978d+0.085 are satisfied.

[0066] The upper limit of q in each of (A) to (E) means a threshold value that satisfies the condition that, when d is the lower limit value, the rate of change of the sound speed in the edge region 22 relative to the sound speed in the inner region 23 is 1% or less. The lower limit of q in each of (A) to (E) means a threshold value that satisfies the condition that, when d is the upper limit value, the rate of change is -1% or more. By appropriately changing q based on the characteristics of 507 to 513 and obtaining characteristics, a person skilled in the art can derive an appropriate numerical range of q in each of (A) to (E) for the conditions of d given in each of (A) to (E).

[0067] If the rate of change of the sound velocity in the edge region 22 relative to the sound velocity in the inner region 23 exceeds 1%, the phase disturbance of the impedance with respect to the frequency may become large and the frequency characteristics may deteriorate in the second frequency band. If the rate of change is below 0% or even -1%, ripples may occur in the frequency characteristics in the first frequency band, and the phase disturbance of the impedance with respect to the frequency may become large and the frequency characteristics may deteriorate.

[0068] Fig. 18 and Fig. 19 are graphs showing good frequency characteristics in the LT model. Fig. 20 and Fig. 21 are graphs showing good frequency characteristics in the LN model. Fig. 22 to Fig. 37 are graphs showing frequency characteristics of the LT model. Fig. 38 to Fig. 45 are graphs showing frequency characteristics of the LN model.

[0069] The following rules are set for the notation of simulation conditions in Figures 18 to 45. In Figures 18 to 45, simulation conditions are notated in the order of X1 to X4 along with the corresponding line type notation. For examples of X1 to X4, see Figures 18 and 22.

[0070] X1: If the material of the dielectric layer 3 is AlN, it is written as "AlN", if it is SiO2, it is written as "SiO2", if it is Ta2O5, it is written as "Ta2O5" X2: Thickness T3 is B times thickness T1, and is written as "(thickness Bt)" X3: The difference between the duty of the first electrode finger 8 and the second electrode finger 9 in the inner region 23 and the duty of the first electrode finger 8 and the second electrode finger 9 in the edge region 22 is C, which is expressed as "IDT tip duty: -C." However, if the difference is 0, this is expressed as "IDT tip duty: no change." X4: If the IDT electrode 2 does not have a dummy electrode 20, it is indicated as "no dummy", if it has a finger-shaped dummy electrode, it is indicated as "with dummy", and if it has a planar dummy electrode, it is indicated as "solid dummy". The definitions of X1 to X4 are as described above. For convenience of explanation, the explanation of the same definitions as those explained above will be omitted.

[0071] 18 to 45 show frequency characteristics under the consistent assumption that, in plan view, dielectric layer 3 overlaps tip portion 11 and gap 13, and also overlaps dummy electrode 20 when dummy electrode 20 is located in gap 13. In addition, conditions not described above are also consistent among all characteristics in Figs. 18 to 45.

[0072] 26 and 27, and 36 and 37, if the duty factor of the first electrode finger 8 and the second electrode finger 9 in edge region 22 is too small, the frequency characteristics in the third frequency band tend to improve while the frequency characteristics in the first frequency band tend to deteriorate. There is a trade-off between the effect of improving the frequency characteristics in the third frequency band and the effect of improving the frequency characteristics in the first frequency band. For this reason, it can be seen that there are optimal conditions for both thickness T3 and the difference between the duty factors of the first electrode finger 8 and the second electrode finger 9 in inner region 23 and the duty factors of the first electrode finger 8 and the second electrode finger 9 in edge region 22.

[0073] [Embodiment 2] Fig. 46 is a cross-sectional view showing a schematic configuration of an acoustic wave device 101 according to a second embodiment of the present disclosure. As shown in Fig. 46, the acoustic wave device 101 may have a membrane structure. The acoustic wave device 101 having a membrane structure shown in Fig. 46 does not need to have a multilayer reflective film 4, and an opening 21 is formed on the piezoelectric body 1 side of the support substrate 5, and the piezoelectric body 1 is provided so as to cover the opening 21.

[0074] [Embodiment 3] 47 is a schematic diagram of a communication device 201 according to a third embodiment of the present disclosure. The communication device 201 is an application example of the acoustic wave device 101, and performs wireless communication using radio waves. The communication device 201 may include a transmit filter 111 and a receive filter 112. Each of the transmit filter 111 and the receive filter 112 may include the acoustic wave device 101.

[0075] In the communication device 201, a transmission information signal TIS including information to be transmitted may be modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency-Integrated Circuit) 113, and converted into a transmission signal TS. A band-pass filter 114 may remove unnecessary components from the transmission signal TS that are not in the transmission passband. Next, the transmission signal TS after removing the unnecessary components may be amplified by an amplifier 115 and input to the transmission filter 111.

[0076] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via the antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 201.

[0077] Furthermore, the antenna 116 may convert the received radio wave from the outside into a received signal RS, which is an electric signal, and input the received signal RS to the receiving filter 112 via the antenna terminal. The receiving filter 112 may remove unnecessary components outside the receiving passband from the input received signal RS. The receiving filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receiving passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0078] The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) containing appropriate information. For example, the transmission information signal TIS and the reception information signal RIS may be analog voice signals or digitalized voice signals. The passband of the wireless signal may be set appropriately and may conform to various known standards.

[0079] 〔summary〕 The acoustic wave device according to a first aspect of the present disclosure has a piezoelectric body, a first electrode finger, a second electrode finger adjacent to the first electrode finger, and a bus bar electrically connected to the second electrode finger, and comprises an IDT electrode located above the piezoelectric body, and a dielectric layer located above the IDT electrode, wherein the thickness of the piezoelectric body is less than twice the pitch of the first electrode finger and the second electrode finger, the first electrode finger includes a slender portion located at the tip of the first electrode finger and a non-fine portion located closer to the base of the first electrode finger than the slender portion, and the dielectric layer includes a first region that overlaps with at least a portion of the slender portion in a planar view and does not overlap with at least a portion of the non-fine portion in the planar view.

[0080] The acoustic wave device according to aspect 2 of the present disclosure is similar to aspect 1, in that, in the planar view, the dielectric layer includes a second region overlapping the gap between the first electrode finger and the bus bar, and a third region overlapping the bus bar.

[0081] A third aspect of the present disclosure relates to an acoustic wave device according to the first or second aspect, wherein the dielectric layer includes at least one of a high acoustic velocity dielectric material and Ta2O5.

[0082] A fourth aspect of the present disclosure relates to an acoustic wave device according to the third aspect, wherein the high acoustic velocity dielectric material is any one of SiO2, AlN, SiN, Al2O3, and TiO2.

[0083] A fifth aspect of the present disclosure relates to an acoustic wave device in any one of the first to fourth aspects, wherein the thickness of the dielectric layer is not less than 0.015 times and not more than 0.1 times the thickness of the piezoelectric body.

[0084] An acoustic wave device according to a sixth aspect of the present disclosure is any one of the first to fifth aspects, wherein the length of the tip portion of the first electrode finger in the longitudinal direction is greater than or equal to the thickness of the piezoelectric body and is less than or equal to five times the thickness of the piezoelectric body.

[0085] An acoustic wave device according to a seventh aspect of the present disclosure is, in any one of the first to sixth aspects, an edge region that includes the slender portion and extends in the arrangement direction of the first electrode fingers, and an inner region that includes the non-detailed portion and is located inside the edge region among the intersection regions of the first electrode fingers and the second electrode fingers, wherein the difference between the duty cycles of the first electrode fingers and the second electrode fingers in the inner region and the duty cycles of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.03 and less than or equal to 0.3.

[0086] An acoustic wave device according to an eighth aspect of the present disclosure is the acoustic wave device of any one of the first to seventh aspects, further comprising a low acoustic impedance layer and a high acoustic impedance layer located below the piezoelectric body.

[0087] A ninth aspect of the present disclosure relates to an acoustic wave device according to any one of the first to eighth aspects, wherein the piezoelectric body includes at least one of LiTaO3 and LiNbO3.

[0088] In the acoustic wave device of aspect 10 of the present disclosure, when an edge region is an area that includes the slender portion and extends in the arrangement direction of the first electrode fingers, and an inner region is an area that includes the non-detailed portion and is located inside the edge region among the intersection regions of the first electrode fingers and the second electrode fingers, the absolute value of the rate of change of the sound speed in the edge region relative to the sound speed in the inner region is 1% or less.

[0089] An acoustic wave device according to an eleventh aspect of the present disclosure is, in the tenth aspect, wherein the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is AlN, a ratio of a thickness of the dielectric layer to a thickness of the piezoelectric body is defined as d, and a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 3.387d-0.106≧q≧3.300d+0.133 Satisfy.

[0090] An acoustic wave device according to a twelfth aspect of the present disclosure is, in the tenth aspect, wherein the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is SiO2, a ratio of a thickness of the dielectric layer to a thickness of the piezoelectric body is defined as d, and a difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 3.113d-0.124≧q≧2.814d+0.142 Satisfy.

[0091] An acoustic wave device according to a thirteenth aspect of the present disclosure is the same as in the tenth aspect, except that the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is Ta2O5, a ratio of a thickness of the dielectric layer to a thickness of the piezoelectric body is defined as d, and a difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.0125≦d≦0.035 and 10.694d-0.135≧q≧10.196d+0.131 Satisfy.

[0092] An acoustic wave device according to a fourteenth aspect of the present disclosure is the same as in the tenth aspect, except that the material of the piezoelectric body is LiNbO3, the material of the dielectric layer is SiO2, a ratio of a thickness of the dielectric layer to a thickness of the piezoelectric body is defined as d, and a difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 1.312d-0.028≧q≧0.790d+0.113 Satisfy.

[0093] An acoustic wave device according to a fifteenth aspect of the present disclosure is the same as in the tenth aspect, except that the material of the piezoelectric body is LiNbO3, the material of the dielectric layer is Ta2O5, a ratio of a thickness of the dielectric layer to a thickness of the piezoelectric body is defined as d, and a difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.01≦d≦0.035 and 5.566d-0.050≧q≧3.978d+0.085 Satisfy.

[0094] An acoustic wave device according to aspect 16 of the present disclosure is such that, in aspect 1, the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is AlN, the thickness of the dielectric layer is greater than or equal to 0.075 x 0.85 times the thickness of the piezoelectric body and less than or equal to 0.075 x 1.15 times the thickness of the piezoelectric body, and when viewed in the planar view, the dielectric layer overlaps with the first electrode finger and the gap between the bus bar, and includes the slender portion, and when a region extending in the arrangement direction of the first electrode finger is defined as an edge region, and includes the non-detailed portion, and when a region of the intersection region of the first electrode finger and the second electrode finger that is located more inside the edge region is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is greater than or equal to 0.18 x 0.75 and less than 0.18 x 1.25.

[0095] An acoustic wave device according to a seventeenth aspect of the present disclosure is the acoustic wave device of the first aspect, wherein the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is AlN, the thickness of the dielectric layer is 0.075×0.85 times or more the thickness of the piezoelectric body and is 0.075×1.15 times or less the thickness of the piezoelectric body, the dielectric layer overlaps the gap between the first electrode finger and the bus bar in the planar view, and the IDT electrode is located in the gap and overlaps the dielectric layer in the planar view. When a region that does not have a dummy electrode, includes the slender portion, and extends in the arrangement direction of the first electrode fingers is defined as an edge region, and a region that includes the non-detailed portion and is located inside the edge region among the intersection regions of the first electrode fingers and the second electrode fingers is defined as an inner region, the difference between the duty of the first electrode fingers and the second electrode fingers in the inner region and the duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.27×0.75 and less than or equal to 0.27×1.25.

[0096] An acoustic wave device according to an eighteenth aspect of the present disclosure is the acoustic wave device of the first aspect, wherein a material of the piezoelectric body is LiTaO3, a material of the dielectric layer is SiO2, a thickness of the dielectric layer is 0.075×0.85 times or more the thickness of the piezoelectric body and is 0.075×1.15 times or less the thickness of the piezoelectric body, the dielectric layer overlaps a gap between the first electrode finger and the bus bar in the planar view, and the IDT electrode is located in the gap and overlaps the dielectric layer in the planar view. The dummy electrode has a dummy electrode having a structure as described above, and when a region including the slender portion and extending in the arrangement direction of the first electrode finger is defined as an edge region, and a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is greater than or equal to 0.18×0.75 and less than or equal to 0.18×1.25.

[0097] A nineteenth aspect of the present disclosure relates to an acoustic wave device according to the eighteenth aspect, wherein the dummy electrode is a planar dummy electrode.

[0098] An acoustic wave device according to aspect 20 of the present disclosure is, in aspect 1, wherein the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is Ta2O5, the thickness of the dielectric layer is greater than or equal to 0.025×0.85 times the thickness of the piezoelectric body and less than or equal to 0.025×1.15 times the thickness of the piezoelectric body, and when viewed in the planar view, the dielectric layer overlaps with the first electrode finger and the gap between the bus bar, and includes the slender portion, and when a region extending in the arrangement direction of the first electrode finger is defined as an edge region, and includes the non-detailed portion, and when a region of the intersection region of the first electrode finger and the second electrode finger that is located more inside the edge region is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is greater than or equal to 0.18×0.75 and less than 0.18×1.25.

[0099] An acoustic wave device according to a twenty-first aspect of the present disclosure is similar to the twenty-first aspect, except that the IDT electrode has a planar dummy electrode located in the gap and overlapping with the dielectric layer in the planar view.

[0100] An acoustic wave device according to a twenty-second aspect of the present disclosure is the acoustic wave device of the first aspect, wherein the material of the piezoelectric body is LiTaO3, the material of the dielectric layer is Ta2O5, the thickness of the dielectric layer is 0.025×0.85 times or more the thickness of the piezoelectric body and 0.025×1.15 times or less the thickness of the piezoelectric body, the dielectric layer overlaps the gap between the first electrode finger and the bus bar in the planar view, and the IDT electrode is located in the gap and overlaps the dielectric layer in the planar view. When a region that does not have a dummy electrode, includes the slender portion, and extends in the arrangement direction of the first electrode finger is defined as an edge region, and a region that includes the non-detailed portion and is located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is 0.27×0.75 or more and 0.27×1.25 or less.

[0101] An acoustic wave device according to a twenty-third aspect of the present disclosure is the acoustic wave device of the first aspect, wherein a material of the piezoelectric body is LiNbO3, a material of the dielectric layer is SiO2, a thickness of the dielectric layer is 0.080×0.85 times or more the thickness of the piezoelectric body and is 0.080×1.15 times or less the thickness of the piezoelectric body, the dielectric layer overlaps a gap between the first electrode finger and the bus bar in the planar view, and the IDT electrode is located in the gap and is in contact with the dielectric layer in the planar view. When an area that does not have an overlapping dummy electrode, includes the slender portion, and extends in the arrangement direction of the first electrode finger is defined as an edge area, and an area that includes the non-detailed portion and is located inside the edge area within the intersection area of ​​the first electrode finger and the second electrode finger is defined as an inner area, the difference between the duty of the first electrode finger and the second electrode finger in the inner area and the duty of the first electrode finger and the second electrode finger in the edge area is 0.1 x 0.75 or more and 0.1 x 1.25 or less.

[0102] An acoustic wave device according to aspect 24 of the present disclosure is, in aspect 1, wherein the material of the piezoelectric body is LiNbO3, the material of the dielectric layer is Ta2O5, the thickness of the dielectric layer is greater than or equal to 0.027 x 0.85 times the thickness of the piezoelectric body and less than or equal to 0.027 x 1.15 times the thickness of the piezoelectric body, and when viewed in the planar view, the dielectric layer overlaps with the first electrode finger and the gap between the bus bar, and includes the slender portion, and when a region extending in the arrangement direction of the first electrode finger is defined as an edge region, and includes the non-detailed portion, and when a region of the intersection region of the first electrode finger and the second electrode finger that is located more inside the edge region is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is greater than or equal to 0.1 x 0.75 and less than 0.1 x 1.25.

[0103] A twenty-fifth aspect of the present disclosure relates to an acoustic wave device according to the first aspect, wherein the material of the piezoelectric body is LiNbO3, the material of the dielectric layer is Ta2O5, the thickness of the dielectric layer is 0.020×0.85 times or more the thickness of the piezoelectric body and 0.020×1.15 times or less the thickness of the piezoelectric body, the dielectric layer overlaps the gap between the first electrode finger and the bus bar in the planar view, and the IDT electrode is located in the gap and overlaps the dielectric layer in the planar view. When a region that does not have a dummy electrode, includes the slender portion, and extends in the arrangement direction of the first electrode finger is defined as an edge region, and a region that includes the non-detailed portion and is located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger is defined as an inner region, the difference between the duty of the first electrode finger and the second electrode finger in the inner region and the duty of the first electrode finger and the second electrode finger in the edge region is 0.06×0.75 or more and 0.06×1.25 or less.

[0104] An acoustic wave device according to a twenty-sixth aspect of the present disclosure is configured in any one of the first to twenty-fifth aspects to excite an antisymmetric A1 mode.

[0105] An acoustic wave device according to a twenty-seventh aspect of the present disclosure is in any one of the first to twenty-fifth aspects, in which a bulk wave is excited.

[0106] The acoustic wave device according to a twenty-eighth aspect of the present disclosure is in any one of the first to twenty-seventh aspects, which has a membrane structure.

[0107] A communication device according to a twenty-ninth aspect of the present disclosure includes the acoustic wave device according to any one of the first to twenty-eighth aspects.

[0108] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure.

[0109] For example, the acoustic wave device 101 may have a typical additional structure.

[0110] For example, there may be a protective film that protects the acoustic wave device 101 from moisture and the like. The protective film covers, for example, the entire IDT electrode 2, the piezoelectric body 1, and the dielectric layer 3. The protective film covers the IDT electrode 2 and the piezoelectric body 1, and the dielectric layer 3 may be provided above the protective film.

[0111] For example, various sound velocity adjustment means may be employed to set the absolute value of the rate of change of the sound velocity in edge region 22 relative to the sound velocity in inner region 23 to 1% or less. For example, slender portion 19 may be provided on both tip end 11 of first electrode finger 8 and base side of second electrode finger 9, or on either one of them. For example, the thickness of IDT electrode 2 may be made thinner at the location where dielectric film 3 overlaps. Or, the thickness of IDT electrode 2 may be made thicker at the location where dielectric film 3 does not overlap. [Explanation of symbols]

[0112] 1 Piezoelectric 2 IDT electrode 3 Dielectric Layer 4 Multilayer reflective film 5 Support substrate 6. Low acoustic impedance layer 7 High acoustic impedance layer 8 1st electrode finger 9 Second electrode finger 10 Busbar 11 Tip of first electrode finger 12 First area 13 Gap between first electrode finger and bus bar 14 Second area 15 Third area 16 Center of the first electrode finger in the D1 direction 17 Center of the second electrode finger in the D1 direction 18 Non-detail 19 Slim Section 20 Dummy electrode 21 Opening 22 Edge Area 23 Inner area 101 Acoustic Wave Devices 201 Communication equipment p Pitch of the first and second electrode fingers L11: Length of the tip of the first electrode finger in the longitudinal direction T1 Thickness of the piezoelectric element T3 Dielectric layer thickness W18 Non-detailed width W19 Width of narrow part

Claims

1. A piezoelectric body; an IDT electrode having first electrode fingers, second electrode fingers adjacent to the first electrode fingers, and a bus bar electrically connected to the second electrode fingers, the IDT electrode being located in a layer above the piezoelectric body; a dielectric layer located above the IDT electrode, a thickness of the piezoelectric body is equal to or smaller than twice the pitch of the first electrode fingers and the second electrode fingers; The first electrode finger is a slender portion located at a tip of the first electrode finger; a non-detailed portion located closer to a base of the first electrode finger than the slender portion, An acoustic wave device, wherein the dielectric layer includes a first region that overlaps at least a portion of the thin portion in a plan view and does not overlap at least a portion of the non-fine portion in the plan view.

2. 2. The acoustic wave device according to claim 1, wherein, in the planar view, the dielectric layer includes a second region overlapping the gap between the first electrode finger and the bus bar, and a third region overlapping the bus bar.

3. The dielectric layer is made of a high acoustic velocity dielectric material and Ta. ２ O ５ The acoustic wave device of claim 1 , comprising at least one of:

4. The high acoustic velocity dielectric material is SiO ２ , AlN, SiN, Al ２ O ３ , and TiO ２ 4. The acoustic wave device according to claim 3, wherein

5. The acoustic wave device according to claim 1 , wherein the thickness of the dielectric layer is not less than 0.015 times and not more than 0.1 times the thickness of the piezoelectric body.

6. The acoustic wave device according to claim 1 , wherein a length of the tip portion of the first electrode finger in the longitudinal direction is equal to or greater than a thickness of the piezoelectric body and is equal to or less than five times the thickness of the piezoelectric body.

7. a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, The acoustic wave device according to claim 1 , wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is not less than 0.03 and not more than 0.

3.

8. The acoustic wave device according to claim 1 , further comprising a low acoustic impedance layer and a high acoustic impedance layer located below the piezoelectric body.

9. The piezoelectric body is LiTaO ３ and LiNbO ３ The acoustic wave device of claim 1 , comprising at least one of:

10. a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, The acoustic wave device according to claim 1 , wherein an absolute value of a rate of change of the sound velocity in the edge region relative to the sound velocity in the inner region is 1% or less.

11. The material of the piezoelectric body is LiTaO ３ and the material of the dielectric layer is AlN; The ratio of the thickness of the dielectric layer to the thickness of the piezoelectric body is defined as d, When a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 3.387d-0.106≧q≧3.300d+0.133 The acoustic wave device according to claim 10 , wherein

12. The material of the piezoelectric body is LiTaO ３ and The material of the dielectric layer is SiO ２ and The ratio of the thickness of the dielectric layer to the thickness of the piezoelectric body is defined as d, When a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 3.113d-0.124≧q≧2.814d+0.142 The acoustic wave device according to claim 10 , wherein

13. The material of the piezoelectric body is LiTaO ３ and The material of the dielectric layer is Ta. ２ O ５ and The ratio of the thickness of the dielectric layer to the thickness of the piezoelectric body is defined as d, When a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.0125≦d≦0.035 and 10.694d-0.135≧q≧10.196d+0.131 The acoustic wave device according to claim 10 , wherein

14. The material of the piezoelectric body is LiNbO ３ and The material of the dielectric layer is SiO ２ and The ratio of the thickness of the dielectric layer to the thickness of the piezoelectric body is defined as d, When a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.05≦d≦0.1 and 1.312d-0.028≧q≧0.790d+0.113 The acoustic wave device according to claim 10 , wherein

15. The material of the piezoelectric body is LiNbO ３ and The material of the dielectric layer is Ta. ２ O ５ and The ratio of the thickness of the dielectric layer to the thickness of the piezoelectric body is defined as d, When a difference between a duty of the first electrode finger and the second electrode finger in the inner region and a duty of the first electrode finger and the second electrode finger in the edge region is defined as q, 0.01≦d≦0.035 and 5.566d-0.050≧q≧3.978d+0.085 The acoustic wave device according to claim 10 , wherein

16. The material of the piezoelectric body is LiTaO ３ and the material of the dielectric layer is AlN; the thickness of the dielectric layer is equal to or greater than 0.075×0.85 times the thickness of the piezoelectric body and equal to or less than 0.075×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with the first electrode finger and the gap between the bus bar in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.18×0.75 and less than or equal to 0.18×1.

25.

17. The material of the piezoelectric body is LiTaO ３ and the material of the dielectric layer is AlN; the thickness of the dielectric layer is equal to or greater than 0.075×0.85 times the thickness of the piezoelectric body and equal to or less than 0.075×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, the IDT electrode does not include a dummy electrode located in the gap and overlapping with the dielectric layer in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.27×0.75 and less than or equal to 0.27×1.

25.

18. The material of the piezoelectric body is LiTaO ３ and The material of the dielectric layer is SiO ２ and the thickness of the dielectric layer is equal to or greater than 0.075×0.85 times the thickness of the piezoelectric body and equal to or less than 0.075×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, the IDT electrode has a dummy electrode located in the gap and overlapping with the dielectric layer in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.18×0.75 and less than or equal to 0.18×1.

25.

19. The acoustic wave device according to claim 18 , wherein the dummy electrode is a planar dummy electrode.

20. The material of the piezoelectric body is LiTaO ３ and The material of the dielectric layer is Ta. ２ O ５ and the thickness of the dielectric layer is equal to or greater than 0.025×0.85 times the thickness of the piezoelectric body and equal to or less than 0.025×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.18×0.75 and less than or equal to 0.18×1.

25.

21. The acoustic wave device according to claim 20 , wherein the IDT electrode includes a planar dummy electrode located in the gap and overlapping with the dielectric layer in the planar view.

22. The material of the piezoelectric body is LiTaO ３ and The material of the dielectric layer is Ta. ２ O ５ and the thickness of the dielectric layer is equal to or greater than 0.025×0.85 times the thickness of the piezoelectric body and equal to or less than 0.025×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, the IDT electrode does not include a dummy electrode located in the gap and overlapping with the dielectric layer in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.27×0.75 and less than or equal to 0.27×1.

25.

23. The material of the piezoelectric body is LiNbO ３ and The material of the dielectric layer is SiO ２ and the thickness of the dielectric layer is equal to or greater than 0.080×0.85 times the thickness of the piezoelectric body and equal to or less than 0.080×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, the IDT electrode does not include a dummy electrode located in the gap and overlapping with the dielectric layer in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is 0.1 x 0.75 or more and 0.1 x 1.25 or less.

24. The material of the piezoelectric body is LiNbO ３ and The material of the dielectric layer is Ta. ２ O ５ and the thickness of the dielectric layer is equal to or greater than 0.027×0.85 times the thickness of the piezoelectric body and equal to or less than 0.027×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is 0.1 x 0.75 or more and 0.1 x 1.25 or less.

25. The material of the piezoelectric body is LiNbO ３ and The material of the dielectric layer is Ta. ２ O ５ and the thickness of the dielectric layer is equal to or greater than 0.020×0.85 times the thickness of the piezoelectric body and equal to or less than 0.020×1.15 times the thickness of the piezoelectric body; the dielectric layer overlaps with a gap between the first electrode finger and the bus bar in the plan view, the IDT electrode does not include a dummy electrode located in the gap and overlapping with the dielectric layer in the plan view, a region including the slender portion and extending in an arrangement direction of the first electrode fingers is defined as an edge region; When an inner region is defined as a region including the non-detailed portion and located inside the edge region among the intersection regions of the first electrode finger and the second electrode finger, 2. The acoustic wave device according to claim 1, wherein a difference between a duty of the first electrode fingers and the second electrode fingers in the inner region and a duty of the first electrode fingers and the second electrode fingers in the edge region is greater than or equal to 0.06 x 0.75 and less than or equal to 0.06 x 1.

25.

26. Antisymmetric mode A １ The acoustic wave device of claim 1 , wherein the acoustic wave device excites a mode.

27. The acoustic wave device of claim 1 , which excites bulk waves.

28. The acoustic wave device of claim 1 , which is a membrane structure.

29. A communication device comprising an acoustic wave device according to any one of claims 1 to 28.

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