Elastic wave device and filter device

Abstract

An elastic wave device 1 according to the present invention comprises a support member 3, a piezoelectric film including a piezoelectric layer 6, and at least one IDT electrode 7 having a plurality of electrode fingers. In the at least one IDT electrode 7, the electrode finger pitches and / or the widths of the electrode fingers vary. When one electrode finger pitch is denoted as P1 and the other electrode finger pitch is denoted as P2 in three continuous electrode fingers, and Mmax represents the widest width and Mmin represents the narrowest width among the widths of the three continuous electrode fingers, an adjacent chirp rate represented by at least one of formulae (1) and (2) is larger than 0° in at least a part of the at least one IDT electrode 7. In the entirety of the IDT electrode 7, an adjacent chirp rate represented by each of formulae (1) and (2) is 0.6° or less.　(1): Arctan [|P1-P2| / (P1+P2)] (2): Arctan [|Mmax-Mmin| / (P1+P2)]

Description

Elastic wave device and filter device

[0001] The present invention relates to an acoustic wave device and a filter device.

[0002] Conventionally, acoustic wave devices have been widely used in filters for mobile phones and the like. Recently, an acoustic wave device using thickness-shear mode bulk waves has been proposed, as described in Patent Document 1 below. In this acoustic wave device, a piezoelectric layer is provided on a support. An IDT (Interdigital Transducer) electrode having a plurality of electrode fingers is provided on the piezoelectric layer. Adjacent electrode fingers in the IDT electrode are connected to different potentials. By applying an AC voltage between the adjacent electrode fingers, thickness-shear mode bulk waves are excited.

[0003] In the above-described acoustic wave device, two types of regions having different electrode finger pitches and different electrode finger widths are arranged alternately, thereby suppressing unwanted waves.

[0004] US Patent Application Publication No. 2021 / 0067138

[0005] However, in the acoustic wave device described in Patent Document 1, parameters are not set taking into consideration wave leakage and energy distortion, which may result in insufficient reduction of loss or sufficient enhancement of power durability.

[0006] An object of the present invention is to provide an acoustic wave device and a filter device that can reduce loss and increase power durability.

[0007] An elastic wave device according to one embodiment of the present invention includes a support member, a piezoelectric film provided on the support member and including a piezoelectric layer, and at least one IDT electrode provided on the piezoelectric film and having a plurality of electrode fingers, wherein an acoustic reflector is provided on the support member at a position overlapping with at least one of the IDT electrodes in a plan view, and wherein, when the thickness of the piezoelectric film is d and the average value of the electrode finger pitch in the IDT electrode is P0, d / P0 is 0.5 or less in the at least one IDT electrode, and the electrode finger pitch in the at least one IDT electrode is At least one of the pitch of the IDT electrodes and the width of the electrode fingers varies, and when one electrode finger pitch is P1 and the other electrode finger pitch is P2 among three consecutive electrode fingers, and the widest width of the three consecutive electrode fingers is Mmax and the narrowest width is Mmin, in at least a part of the at least one IDT electrode, the adjacent chirp rate expressed by at least one of the following equations (1) and (2) is greater than 0°, and in the entire IDT electrode, the adjacent chirp rate expressed by both of the following equations (1) and (2) is 0.6° or less: Arctan[|P1-P2| / (P1+P2)] ...equation (1) Arctan[|Mmax-Mmin| / (P1+P2)] ...equation (2)

[0008] In one broad aspect, a filter device according to the present invention includes a plurality of resonators, the plurality of resonators including at least one series arm resonator and at least one parallel arm resonator, and at least one of the plurality of resonators is an elastic wave device configured according to the present invention.

[0009] In another broad aspect of the present invention, a filter device includes an elastic wave device configured according to the present invention and at least one resonator other than the two elastic wave resonators in the elastic wave device, wherein the two elastic wave resonators are either series arm resonators connected in parallel to each other or parallel arm resonators connected in parallel to each other.

[0010] According to the acoustic wave device and the filter device of the present invention, loss can be reduced and power durability can be increased.

[0011] FIG. 1 is a schematic plan view of an elastic wave device according to a first preferred embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line II in FIG. 1. FIGS. 3A and 3B are schematic diagrams illustrating the adjacent chirp rate. FIGS. 4A and 4B are diagrams illustrating the chirp intensity. FIG. 5 is a diagram illustrating the relationship between the electrode finger pitch and the position of an IDT electrode in the direction perpendicular to the electrode fingers for levels 1 to 11. FIG. 6 is a diagram illustrating the relationship between the adjacent chirp rate and the external displacement ratio. FIG. 7 is a diagram illustrating the relationship between the adjacent chirp rate and the electrode finger displacement ratio. FIG. 8 is a diagram illustrating the relationship between the adjacent chirp rate and chirp intensity, and the impedance-frequency characteristics in a parallel arm resonator. FIG. 9 is a diagram illustrating the relationship between the adjacent chirp rate and chirp intensity, and the impedance-frequency characteristics in a series arm resonator. FIG. 10 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention. FIG. 11 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention. FIG. 12 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention. FIG. 13 is a schematic cross-sectional view taken along line II in FIG. 12 . FIG. 14 is a diagram showing the relationship between the position of the IDT electrode in the direction orthogonal to the electrode fingers and the width of the electrode fingers for levels 1 to 11. FIG. 15 is a diagram showing the relationship between the adjacent chirp rate and the external displacement ratio. FIG. 16 is a diagram showing the relationship between the adjacent chirp rate and the electrode finger displacement ratio. FIG. 17 is a diagram showing the relationship between the adjacent chirp rate and chirp intensity in a parallel arm resonator and the impedance-frequency characteristics. FIG. 18 is a diagram showing the relationship between the adjacent chirp rate and chirp intensity in a series arm resonator and the impedance-frequency characteristics. FIG. 19 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention. FIG. 20 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention. FIG. 21 is a schematic plan view of an elastic wave device according to a seventh preferred embodiment of the present invention. FIG. 22 is a schematic front cross-sectional view of an elastic wave device according to an eighth preferred embodiment of the present invention. 23 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention, and FIG. 24A is a diagram showing the relationship between the position of an IDT electrode in the direction orthogonal to the electrode fingers and the electrode finger pitch in one elastic wave resonator according to the ninth preferred embodiment of the present invention.FIG. 24(b) is a diagram showing the relationship between the position of the IDT electrode in the electrode finger orthogonal direction and the electrode finger pitch in the other acoustic wave resonator according to the ninth embodiment of the present invention. FIG. 25(a) is a diagram showing the relationship between the position of the IDT electrode in the electrode finger orthogonal direction and the electrode finger width in one acoustic wave resonator according to the tenth embodiment of the present invention. FIG. 25(b) is a diagram showing the relationship between the position of the IDT electrode in the electrode finger orthogonal direction and the electrode finger width in the other acoustic wave resonator according to the tenth embodiment of the present invention. FIG. 26 is a circuit diagram of a filter device according to an eleventh embodiment of the present invention. FIG. 27 is a circuit diagram of a filter device according to a modification of the eleventh embodiment of the present invention. FIG. 28 is a diagram showing the relationship between d / P0 and the fractional bandwidth of an acoustic wave resonator. FIG. 29 is a diagram showing the relationship between the fractional bandwidth and the magnitude of normalized spurious signals in an acoustic wave resonator. FIG. 30 is a diagram showing the relationship between d / P0, the metallization ratio MR, and the fractional bandwidth. FIG. 31 is a diagram showing LiNbO when d / P0 is set as close to 0 as possible. ３ FIG. 10 is a diagram showing a map of fractional bandwidths versus Euler angles (0°, θ, ψ) of the .lambda.

[0012] The present invention will be clarified below by describing specific embodiments of the present invention with reference to the drawings.

[0013] It should be noted that the embodiments described in this specification are merely examples, and partial substitution or combination of configurations is possible between different embodiments.

[0014] Fig. 1 is a schematic plan view of an elastic wave device according to a first preferred embodiment of the present invention, and Fig. 2 is a schematic cross-sectional view taken along line II in Fig. 1.

[0015] As shown in FIG. 1 , the acoustic wave device 1 includes a piezoelectric substrate 2 and an IDT electrode 7. The piezoelectric substrate 2 is a substrate having piezoelectric properties. As shown in FIG. 2 , the piezoelectric substrate 2 includes a support member 3 and a piezoelectric layer 6 serving as a piezoelectric film. The piezoelectric layer 6 is a layer made of a piezoelectric material. However, in this specification, a piezoelectric film refers to a film having piezoelectric properties, and does not necessarily refer to a film made of a piezoelectric material. However, in this embodiment, the piezoelectric film is a single-layer piezoelectric layer 6, which is a film made of a piezoelectric material. Note that in the present invention, the piezoelectric film may be a laminated film including the piezoelectric layer 6.

[0016] In this embodiment, the support member 3 includes a support substrate 4 and an insulating layer 5. The insulating layer 5 is provided on the support substrate 4. A piezoelectric layer 6 is provided on the insulating layer 5. However, the support member 3 may be composed of only the support substrate 4.

[0017] The piezoelectric layer 6 has a first main surface 6 a and a second main surface 6 b. The first main surface 6 a and the second main surface 6 b face each other. Of the first main surface 6 a and the second main surface 6 b, the second main surface 6 b is located on the support member 3 side.

[0018] The support substrate 4 may be made of a semiconductor such as silicon or a ceramic such as aluminum oxide. The insulating layer 5 may be made of an appropriate dielectric such as silicon oxide or tantalum oxide. The piezoelectric layer 6 may be made of LiNbO ３ Alternatively, the material may be made of lithium niobate such as LiTaO ３ In this embodiment, piezoelectric layer 6 is made of lithium niobate. In this specification, a certain component made of a certain material includes a component containing a trace amount of impurities that does not significantly degrade the electrical characteristics of the acoustic wave device.

[0019] A single IDT electrode 7 is provided on a first principal surface 6 a of the piezoelectric layer 6 serving as a piezoelectric film. The elastic wave device 1 of this preferred embodiment is an elastic wave resonator configured to utilize bulk waves in a thickness shear mode. The elastic wave device 1 can be used, for example, as a series arm resonator or a parallel arm resonator in a ladder filter.

[0020] However, in the present invention, multiple IDT electrodes may be provided on the piezoelectric film. This may result in multiple acoustic wave resonators each including an IDT electrode. Thus, the acoustic wave device of the present invention is not limited to a single acoustic wave resonator, but may also be an element having multiple acoustic wave resonators. In this case, the element serving as the acoustic wave device may be used, for example, as part of a filter device.

[0021] As shown in FIG. 1 , the IDT electrode 7 of this embodiment has a pair of bus bars and a plurality of electrode fingers. The pair of bus bars is specifically a first bus bar 16 and a second bus bar 17. The first bus bar 16 and the second bus bar 17 face each other. The plurality of electrode fingers is specifically a plurality of first electrode fingers 18 and a plurality of second electrode fingers 19. One end of each of the plurality of first electrode fingers 18 is connected to the first bus bar 16. One end of each of the plurality of second electrode fingers 19 is connected to the second bus bar 17. The plurality of first electrode fingers 18 and the plurality of second electrode fingers 19 are interdigitated with each other. The first electrode fingers 18 and the second electrode fingers 19 are connected to different potentials. The IDT electrode 7 may be made of a single-layer metal film or a laminated metal film.

[0022] Hereinafter, the first electrode fingers 18 and the second electrode fingers 19 may be collectively referred to simply as electrode fingers. In this specification, the center-to-center distance between adjacent electrode fingers, i.e., the center-to-center distance between adjacent first electrode fingers 18 and second electrode fingers 19, may be referred to as the electrode finger pitch. The direction in which the multiple electrode fingers extend is referred to as the electrode finger extension direction, and the direction perpendicular to the electrode finger extension direction is referred to as the electrode finger perpendicular direction.

[0023] In this embodiment, the width of the electrode fingers in the IDT electrode 7 is constant. The width of the electrode fingers is the dimension along the direction perpendicular to the electrode fingers. On the other hand, the electrode finger pitch in the IDT electrode 7 varies. In other words, the IDT electrode 7 has portions where the electrode finger pitch differs from one another. However, in the present invention, it is sufficient that at least one of the electrode finger pitch and the electrode finger width varies in at least one IDT electrode.

[0024] In this embodiment, the electrode finger pitch increases toward the center of the IDT electrode 7. However, the manner in which the electrode finger pitch changes is not limited to the above.

[0025] 1 , the acoustic wave device 1 has an intersection region F. The intersection region F is a region where the first electrode fingers 18 and the second electrode fingers 19 overlap in the direction perpendicular to the electrode fingers. Hereinafter, the dimension of the intersection region F along the direction in which the electrode fingers extend is referred to as the intersection width.

[0026] The intersection region F includes a plurality of excitation regions C. More specifically, the excitation region C is a region where adjacent first electrode fingers 18 and second electrode fingers 19 overlap in the direction perpendicular to the electrode fingers, and is a region between the centers of the adjacent first electrode fingers 18 and second electrode fingers 19. Note that only two of the plurality of excitation regions C are shown in FIG. 1 .

[0027] The elastic wave device 1 is an elastic wave resonator configured to utilize thickness-shear mode bulk waves as the main mode. By applying an AC voltage to the IDT electrode 7, thickness-shear mode bulk waves are excited in each excitation region C. More specifically, in the elastic wave device 1, where d is the thickness of the piezoelectric film and P0 is the average electrode finger pitch, d / P0 is 0.5 or less. This allows thickness-shear mode bulk waves to be suitably excited in each excitation region C. In this embodiment, the thickness d is the thickness of the piezoelectric layer 6.

[0028] This embodiment is characterized in that it is configured to be able to use a bulk wave in thickness shear mode as the main mode, and that the adjacent chirp rate (described later) is greater than 0° and less than or equal to 0.6° in at least a portion of the IDT electrode 7. This reduces loss and improves power durability. This will be explained below in detail, including the adjacent chirp rate.

[0029] 3A and 3B are schematic diagrams for explaining the adjacent chirp rate.

[0030] 3A, for three consecutive electrode fingers, the electrode finger pitch on one side is P1 and the electrode finger pitch on the other side is P2. The width of the electrode finger at one end of the three consecutive electrode fingers is M1, the width of the central electrode finger is M2, and the width of the electrode finger at the other end is M3. The widest width of the three consecutive electrode fingers is Mmax, and the narrowest width is Mmin.

[0031] In the example shown in FIG. 3( a), the widths of the electrode fingers in the IDT electrode are constant, i.e., M1 = M2 = M3. Therefore, Mmax = Mmin. On the other hand, the electrode finger pitch in the IDT electrode varies. An index indicating the degree to which the electrode finger pitch varies between the centers of adjacent electrode fingers is one of the two concepts of the adjacent chirp rate. The adjacent chirp rate as this index can be expressed by the following equation (1).

[0032] Arctan[|P1-P2| / (P1+P2)]...Formula (1)

[0033] In the example shown in FIG. 3( b), the electrode finger pitch in the IDT electrode is constant, i.e., P1 = P2. However, the width of the electrode fingers in the IDT electrode varies. Specifically, of three consecutive electrode fingers, the width M1 of the electrode finger at one end is the narrowest, and the width M3 of the electrode finger at the other end is the widest. Therefore, M1 = Mmin, and M3 = Mmax. The remaining one of the two concepts of the adjacent chirp rate is an index indicating the degree of width variation among three consecutive electrode fingers. The adjacent chirp rate as this index can be expressed by the following equation (2).

[0034] Arctan[|Mmax−Mmin| / (P1+P2)] …Formula (2)

[0035] The configuration of the first embodiment corresponds to the configuration shown in Fig. 3(a). In the IDT electrode 7 of the first embodiment shown in Fig. 1, the adjacent chirp rate expressed by equation (1) is greater than 0° and is equal to or less than 0.6°. On the other hand, the adjacent chirp rate expressed by equation (2) is 0°.

[0036] In the present invention, it is sufficient that the adjacent chirp rate expressed by at least one of formulas (1) and (2) is greater than 0° in at least a part of the IDT electrode, and that the adjacent chirp rates expressed by both formulas (1) and (2) are 0.6° or less in the IDT electrode.

[0037] While the adjacent chirp rate is a parameter for three consecutive electrode fingers, the chirp intensity is a parameter for the entire IDT electrode. In the following, the longest electrode finger pitch in the entire IDT electrode is defined as Pa_max, and the shortest electrode finger pitch is defined as Pa_min. The widest and narrowest widths of the multiple electrode fingers in the entire IDT electrode are defined as Ma_max and Ma_min, respectively. The average width of the multiple electrode fingers in the IDT electrode is defined as M0.

[0038] 4(a) and 4(b) are diagrams for explaining chirp intensity. Fig. 4(a) shows an example of the relationship between the position of the IDT electrode in the direction perpendicular to the electrode fingers and the electrode finger pitch. Fig. 4(b) shows an example of the relationship between the position of the IDT electrode in the direction perpendicular to the electrode fingers and the electrode finger width.

[0039] The configuration of the example shown in FIG. 4A is the same as that of the first embodiment. Specifically, in the configuration shown in FIG. 4A, the electrode finger pitch value increases toward the center of the IDT electrode. The electrode finger pitch at the center of the IDT electrode is Pa_max. The electrode finger pitch at both ends of the IDT electrode in the direction perpendicular to the electrode fingers is Pa_min. An index indicating the degree of difference between the maximum and minimum electrode finger pitches in the IDT electrode is one of two concepts of chirp intensity. The chirp intensity as this index can be expressed by the following equation (3):

[0040] |Pa_max−Pa_min| / P0…Formula (3)

[0041] In the example shown in FIG. 4( b), the width of the electrode fingers increases toward the center of the IDT electrode. The width of the electrode fingers at the center of the IDT electrode is Ma_max. The width of the electrode fingers at both ends of the IDT electrode in the direction perpendicular to the electrode fingers is Ma_min. An index indicating the degree of difference between the maximum and minimum values ​​of the electrode finger widths in the IDT electrode is the remaining one of the two concepts of chirp strength. Chirp strength as this index can be expressed by the following equation (4).

[0042] |Ma_max−Ma_min| / M0...Formula (4)

[0043] In the configuration of the example shown in Fig. 4(a) or the configuration of the first embodiment, the larger the adjacent chirp rate expressed by equation (1), the larger the chirp intensity expressed by equation (3).On the other hand, in the configuration shown in Fig. 4(b), the larger the adjacent chirp rate expressed by equation (2), the larger the chirp intensity expressed by equation (4).

[0044] In the first embodiment shown in FIG. 1 , a thickness-shear bulk wave can be used as the main mode, the electrode finger pitch is varied in the IDT electrode 7, and the adjacent chirp rate expressed by equation (1) is greater than 0° and less than or equal to 0.6°. This reduces loss and improves power durability. The effects of this are described in detail below.

[0045] 4(a), the displacement was derived by simulation for each change in the adjacent chirp rate expressed by Equation (1) and the chirp intensity expressed by Equation (3). More specifically, the displacement was derived for the area where the electrode fingers are provided, the area between the electrode fingers, and the area outside the IDT electrodes.

[0046] Then, the external displacement ratio was calculated, which is the ratio of the total displacement outside the IDT electrodes to the total displacement in the entire portion where the IDT electrodes are provided. When the total displacement outside the IDT electrodes is O and the total displacement in the entire portion where the IDT electrodes are provided is I, the external displacement ratio is O / I × 100 [%]. The larger the external displacement ratio, the greater the degree of leakage of acoustic wave energy and the greater the loss.

[0047] Furthermore, the electrode finger displacement ratio was calculated, which is the ratio of the total displacement in the portion where the electrode fingers are provided to the total displacement I in the entire portion where the IDT electrodes are provided. When the total displacement in the portion where the electrode fingers are provided is E, the electrode finger displacement ratio is E / I × 100 [%]. The larger the electrode finger displacement ratio, the more likely stress migration occurs when power is applied to the IDT electrodes, and the more likely the IDT electrodes are to deteriorate. In other words, the larger the electrode finger displacement ratio, the lower the power durability.

[0048] The reference design parameters for the configuration shown in FIG. 4(a) in this study are as follows:

[0049] Average electrode finger pitch P0: 4.26 μm Electrode finger width: 0.96 μm Duty ratio: 0.225 Number of electrode fingers: 61 Cross width: 55.11 μm

[0050] In deriving the above displacements and calculating the external displacement ratio and electrode finger displacement ratio, the adjacent chirp rate and chirp intensity were changed as shown in Table 1 from level 1 to level 11. At this time, the electrode finger pitch was changed based on the above-mentioned reference design parameters. The change in the electrode finger pitch for each of levels 1 to 11 is shown in FIG. 5.

[0051]

[0052] 5 is a diagram showing the relationship between the position of the IDT electrode in the direction perpendicular to the electrode fingers and the electrode finger pitch for each of levels 1 to 11. The values ​​on the horizontal axis in Fig. 5 indicate the position of the electrode finger from one end of the IDT electrode in the direction perpendicular to the electrode fingers.

[0053] In level 1, the electrode finger pitch in the IDT electrode remains unchanged. Levels 2 to 7 correspond to the configuration of the first embodiment. On the other hand, levels 8 to 11 do not correspond to the configuration of the first embodiment.

[0054] 6 and 7 are diagrams showing the relationship between the adjacent chirp rate and the external displacement ratio, respectively.

[0055] 6, when the adjacent chirp rate exceeds 0.6°, the external displacement ratio increases at an accelerated rate. On the other hand, when the adjacent chirp rate is 0.6° or less, the external displacement ratio is small. Therefore, by setting the adjacent chirp rate to 0.6° or less, as in the first embodiment, it is possible to suppress energy leakage and reduce loss.

[0056] 7 , when the adjacent chirp rate is 0.6° or less, the electrode finger displacement ratio increases as the adjacent chirp rate increases. On the other hand, when the adjacent chirp rate exceeds 0.6°, the electrode finger displacement ratio fluctuates around a constant value even when the adjacent chirp rate increases. Therefore, by setting the adjacent chirp rate to 0.6° or less, as in the first embodiment, the electrode finger displacement ratio can be reduced and power durability can be improved.

[0057] As described above, it is sufficient that the adjacent chirp rate expressed by at least one of formulas (1) and (2) is greater than 0° in at least a portion of the IDT electrode. However, it is preferable that the adjacent chirp rate expressed by at least one of formulas (1) and (2) is greater than 0° in 20% or more of the entire IDT electrode in the direction perpendicular to the electrode fingers. It is preferable that the adjacent chirp rates expressed by both formulas (1) and (2) are 0.6° or less in the entire IDT electrode. This can more reliably reduce loss and more reliably increase power durability.

[0058] On the other hand, it is preferable that the chirp intensity expressed by at least one of formulas (3) and (4) is 5% or more, thereby making it possible to suppress unwanted waves. This will be described in detail below.

[0059] |Pa_max-Pa_min| / P0...Equation (3) |Ma_max-Ma_min| / M0...Equation (4)

[0060] When the elastic wave device having the configuration example shown in Fig. 4(a) is used as a parallel arm resonator in a ladder filter, the impedance frequency characteristics are derived each time the adjacent chirp rate expressed by Equation (1) and the chirp intensity expressed by Equation (3) are changed. On the other hand, when the elastic wave device having the configuration example shown in Fig. 4(a) is used as a series arm resonator in a ladder filter, the impedance frequency characteristics are derived each time the adjacent chirp rate expressed by Equation (1) and the chirp intensity expressed by Equation (3) are changed.

[0061] In deriving the impedance frequency characteristics, the adjacent chirp rate and chirp intensity were changed as shown in Table 1, from level 1 to level 5.

[0062] Fig. 8 is a diagram showing the relationship between the adjacent chirp rate and chirp intensity, and the impedance frequency characteristics in a parallel arm resonator. Fig. 9 is a diagram showing the relationship between the adjacent chirp rate and chirp intensity, and the impedance frequency characteristics in a series arm resonator.

[0063] As shown in Fig. 8, in the parallel arm resonator, when the chirp intensity is 5% or more, the spurious waves near 3800 MHz, which is lower than the resonance frequency, are suppressed. The spurious waves near 5350 MHz, which is higher than the anti-resonance frequency, are also suppressed. In addition, when the chirp intensity is 10% or more, both types of spurious waves are further suppressed.

[0064] 9, in the series arm resonator, when the chirp intensity is 5% or more, the spurious waves near 5800 MHz, which is higher than the anti-resonance frequency, are also suppressed. When the chirp intensity is 10% or more, the spurious waves are further suppressed.

[0065] As described above, the chirp intensity is preferably 5% or more, and more preferably 10% or more, which enables suppression of unwanted waves whether the acoustic wave device is used as a series arm resonator or a parallel arm resonator.

[0066] The configuration of the first embodiment will be described in more detail below.

[0067] As shown in FIG. 2 , a recess is provided in the insulating layer 5. A piezoelectric layer 6 serving as a piezoelectric film is provided on the insulating layer 5 so as to close the recess. This forms a hollow portion. This hollow portion is the cavity 2a. In the first embodiment, the support member 3 and the piezoelectric film are arranged so that a portion of the support member 3 and a portion of the piezoelectric film face each other with the cavity 2a in between. However, the recess in the support member 3 may be provided across the insulating layer 5 and the support substrate 4. Alternatively, a recess provided only in the support substrate 4 may be closed by the insulating layer 5. The recess may be provided in the piezoelectric layer 6, for example. The cavity 2a may be a through-hole provided in the support member 3.

[0068] In a plan view, at least a portion of the IDT electrode 7 overlaps the cavity 2a of the support member 3. In this specification, a plan view refers to a view from a direction corresponding to the top in FIG. 2 along the stacking direction of the support member 3 and the piezoelectric film. In FIG. 2, for example, of the support substrate 4 side and the piezoelectric layer 6 side, the piezoelectric layer 6 side is the top. Furthermore, in this specification, a plan view is synonymous with a view from the principal surface opposing direction. The principal surface opposing direction is the direction in which the first principal surface 6a and the second principal surface 6b of the piezoelectric layer 6 face each other. More specifically, the principal surface opposing direction is, for example, the normal direction of the first principal surface 6a.

[0069] The cavity 2a shown in Figure 2 is the acoustic reflecting portion of the present invention. The acoustic reflecting portion can reflect the elastic wave toward the piezoelectric layer 6. This allows the energy of the elastic wave to be effectively confined to the piezoelectric layer 6. It is preferable that the multiple excitation regions C overlap with the acoustic reflecting portion in a plan view. This allows the energy of the elastic wave to be more reliably and effectively confined to the piezoelectric layer 6.

[0070] As the acoustic reflecting portion, an acoustic reflecting film (described later) may be provided. For example, an acoustic reflecting film may be provided on the surface of the support member.

[0071] In the first embodiment, the electrode finger pitch value increases toward the center of the IDT electrode 7. In this case, it is easy to reduce the adjacent chirp rate while making it greater than 0°. However, the manner in which the electrode finger pitch changes in the IDT electrode 7 is not limited to the above.

[0072] Here, we present a second and a third embodiment, which differ from the first embodiment only in that the electrode finger pitch in the IDT electrode is changed. In the second and the third embodiments, the adjacent chirp rate expressed by equation (1) is greater than 0°, and the adjacent chirp rates expressed by both equations (1) and (2) are 0.6° or less. This reduces loss and improves power durability.

[0073] FIG. 10 is a schematic plan view of an elastic wave device according to a second preferred embodiment of the present invention.

[0074] In this embodiment, the electrode finger pitch decreases toward the center of the IDT electrode 7 A. In this embodiment, as in the first embodiment, it is easy to reduce the adjacent chirp rate while making the adjacent chirp rate greater than 0°.

[0075] FIG. 11 is a schematic plan view of an elastic wave device according to a third preferred embodiment of the present invention.

[0076] In this embodiment, the electrode finger pitch decreases from one end to the other end of the IDT electrode 7B in the direction perpendicular to the electrode fingers, making it easier to further reduce the adjacent chirp rate while keeping it greater than 0°.

[0077] In the first to third embodiments, the electrode finger pitch is varied in the IDT electrode, but the electrode finger width is not varied. However, in the present invention, it is sufficient that the adjacent chirp rate expressed by at least one of formulas (1) and (2) is greater than 0° in at least a part of the IDT electrode. It is sufficient that the adjacent chirp rate expressed by both formulas (1) and (2) is 0.6° or less in the entire IDT electrode. The fourth embodiment shows an example in which the electrode finger width is varied in the IDT electrode.

[0078] Arctan[|P1-P2| / (P1+P2)]...Equation (1) Arctan[|Mmax-Mmin| / (P1+P2)]...Equation (2)

[0079] Fig. 12 is a schematic plan view of an elastic wave device according to a fourth preferred embodiment of the present invention, and Fig. 13 is a schematic cross-sectional view taken along line II in Fig. 12 .

[0080] 12 and 13 , this embodiment differs from the first embodiment in that the width of the electrode fingers in the IDT electrode 27 varies but the electrode finger pitch does not. That is, this embodiment differs from the first embodiment in that the adjacent chirp rate expressed by equation (1) is 0°. This embodiment also differs from the first embodiment in that the adjacent chirp rate expressed by equation (2) is greater than 0° and equal to or less than 0.6°. Except for the above points, the elastic wave device 21 of this embodiment has a similar configuration to the elastic wave device 1 of the first embodiment.

[0081] The configuration of this embodiment is similar to the example shown in Fig. 4B. More specifically, in acoustic wave device 21, the width of the electrode fingers increases toward the center of IDT electrode 27.

[0082] In this embodiment, as in the first embodiment, it is possible to reduce loss and increase power durability, as will be described in detail below.

[0083] 4(b), the displacement was derived by simulation for each change in the adjacent chirp rate expressed by Equation (2) and the chirp intensity expressed by the following Equation (4). More specifically, the displacement was derived for the area where the electrode fingers are provided, the area between the electrode fingers, and the area outside the IDT electrodes.

[0084] |Ma_max−Ma_min| / M0...Formula (4)

[0085] Then, the external displacement ratio and the electrode finger displacement ratio were calculated. As described above, the external displacement ratio is the ratio of the total displacement O outside the IDT electrodes to the total displacement I in the entire portion where the IDT electrodes are provided, and is O / I × 100 [%]. The electrode finger displacement ratio is the ratio of the total displacement E in the portion where the electrode fingers are provided to the total displacement I in the entire portion where the IDT electrodes are provided, and is E / I × 100 [%]. The reference design parameters for the configuration shown in FIG. 4(b) in this study are as follows:

[0086] Average electrode finger pitch P0: 4.26 μm Electrode finger width: 0.96 μm Duty ratio: 0.225 Number of electrode fingers: 61 Cross width: 55.11 μm

[0087] In deriving the above displacements and calculating the external displacement ratio and electrode finger displacement ratio, the adjacent chirp rate and chirp intensity were varied as shown in Table 2, from level 1 to level 11. At this time, the width of the electrode fingers was varied based on the above-mentioned reference design parameters. The manner in which the width of the electrode fingers changed in each of levels 1 to 11 is shown in FIG. 14.

[0088]

[0089] Fig. 14 is a diagram showing the relationship between the position of the IDT electrode in the direction perpendicular to the electrode fingers and the width of the electrode fingers for each of levels 1 to 11. The values ​​on the horizontal axis in Fig. 14 indicate the position of the electrode finger from one end of the IDT electrode in the direction perpendicular to the electrode fingers.

[0090] In level 1, the width of the electrode fingers in the IDT electrode is unchanged. Levels 2 to 7 correspond to the configuration of the fourth embodiment. On the other hand, levels 8 to 11 do not correspond to the configuration of the fourth embodiment.

[0091] 15 and 16 are diagrams showing the relationship between the adjacent chirp rate and the external displacement ratio, respectively, and the relationship between the adjacent chirp rate and the electrode finger displacement ratio.

[0092] 15, when the adjacent chirp rate exceeds 0.6°, the external displacement ratio is particularly large. On the other hand, when the adjacent chirp rate is 0.6° or less, the external displacement ratio is small. Therefore, by setting the adjacent chirp rate to 0.6° or less, as in the fourth embodiment, it is possible to suppress energy leakage and reduce loss.

[0093] 16 , the electrode finger displacement ratio increases as the adjacent chirp rate increases. The electrode finger displacement ratio increases at an accelerating rate as the adjacent chirp rate exceeds 0.6° and reaches 0.86°. Therefore, by setting the adjacent chirp rate to 0.6° or less, as in the fourth embodiment, the electrode finger displacement ratio can be reduced, thereby improving power durability.

[0094] On the other hand, similarly to when the electrode finger pitch is varied in an IDT electrode, even when the electrode finger width is varied, it is preferable that the chirp intensity be 5% or more. This makes it possible to suppress unwanted waves. This will be explained in detail below.

[0095] When the elastic wave device having the configuration example shown in Fig. 4(b) is used as a parallel arm resonator in a ladder filter, the impedance frequency characteristics are derived each time the adjacent chirp rate expressed by Equation (2) and the chirp intensity expressed by Equation (4) are changed. On the other hand, when the elastic wave device having the configuration example shown in Fig. 4(b) is used as a series arm resonator in a ladder filter, the impedance frequency characteristics are derived each time the adjacent chirp rate expressed by Equation (2) and the chirp intensity expressed by Equation (4) are changed.

[0096] In deriving the impedance frequency characteristics, the adjacent chirp rate and chirp intensity were changed as shown in Table 2, from level 1 to level 5.

[0097] 17 and 18 are graphs showing the relationship between the adjacent chirp rate and chirp strength and the impedance frequency characteristics in a parallel arm resonator, respectively, and the relationship between the adjacent chirp rate and chirp strength and the impedance frequency characteristics in a series arm resonator.

[0098] 17, in the parallel arm resonator, when the chirp intensity is 5% or more, the spurious waves near 3800 MHz, which is lower than the resonance frequency, are suppressed. The spurious waves near 5350 MHz, which is higher than the anti-resonance frequency, are also suppressed. In addition, when the chirp intensity is 10% or more, both types of spurious waves are further suppressed.

[0099] As shown in Figure 18, in the series arm resonator, when the chirp intensity is 5% or more, the spurious waves near 3900 MHz, which is lower than the resonance frequency, are suppressed. The spurious waves near 5800 MHz, which is higher than the anti-resonance frequency, are also suppressed. Furthermore, the spurious waves near 5250 MHz, which is between the resonance frequency and the anti-resonance frequency, are also suppressed. In addition, when the chirp intensity is 10% or more, the three spurious waves are further suppressed. In particular, the spurious waves between the resonance frequency and the anti-resonance frequency are effectively suppressed.

[0100] As described above, the chirp intensity is preferably 5% or more, and more preferably 10% or more, which enables suppression of unwanted waves whether the acoustic wave device is used as a series arm resonator or a parallel arm resonator.

[0101] In the fourth embodiment, the width of the electrode fingers increases toward the center of the IDT electrode 27. In this case, it is easy to reduce the adjacent chirp rate while making it greater than 0°. However, the manner in which the width of the electrode fingers varies in the IDT electrode 27 is not limited to the above.

[0102] Here, we present a fifth and sixth embodiments, which differ from the fourth embodiment only in that the width of the electrode fingers in the IDT electrode is changed. In the fifth and sixth embodiments, the adjacent chirp rate expressed by equation (2) is greater than 0°, and the adjacent chirp rates expressed by both equations (1) and (2) are 0.6° or less. This reduces loss and improves power durability.

[0103] FIG. 19 is a schematic plan view of an elastic wave device according to a fifth preferred embodiment of the present invention.

[0104] In this embodiment, the width of the electrode fingers decreases toward the center of the IDT electrode 27 A. In this embodiment, as in the fourth embodiment, it is easy to reduce the adjacent chirp rate while making the adjacent chirp rate greater than 0°.

[0105] FIG. 20 is a schematic plan view of an elastic wave device according to a sixth preferred embodiment of the present invention.

[0106] In this embodiment, the width of the electrode fingers decreases from one end to the other end of the IDT electrode 27B in the direction perpendicular to the electrode fingers, making it easier to further reduce the adjacent chirp rate while keeping it greater than 0°.

[0107] In the first to sixth embodiments, examples were shown in which either the electrode finger pitch or the electrode finger width is changed in the IDT electrode. As described above, it is sufficient that at least one of the electrode finger pitch and the electrode finger width is changed in the IDT electrode. The seventh embodiment shows an example in which both the electrode finger pitch and the electrode finger width are changed in the IDT electrode.

[0108] FIG. 21 is a schematic plan view of an elastic wave device according to a seventh preferred embodiment of the present invention.

[0109] This embodiment differs from the first embodiment in that both the electrode finger pitch and the electrode finger width are changed in IDT electrode 27C. Except for the above, the elastic wave device of this embodiment has the same configuration as elastic wave device 1 of the first embodiment.

[0110] The IDT electrode 27C has a wide pitch region A1 and a narrow pitch region A2. Specifically, the wide pitch region A1 is a region where the electrode finger pitch is larger than the average electrode finger pitch P0. The narrow pitch region A2 is a region where the electrode finger pitch is smaller than the average electrode finger pitch P0. It should be noted that the IDT electrodes in the first to third embodiments also have a wide pitch region A1 and a narrow pitch region A2.

[0111] In the IDT electrode 27C, the width of the electrode fingers in the wide-pitch region A1 is smaller than the average width M0 of the electrode fingers in the IDT electrode 27C, while the width of the electrode fingers in the narrow-pitch region A2 is larger than the average width M0.

[0112] For example, when the electrode finger pitches of the IDT electrodes of two acoustic wave resonators are different from each other, the resonant frequencies of the main modes are different from each other. Similarly, in the IDT electrodes of one acoustic wave resonator, the resonant frequencies of the main modes are different from each other in regions where the electrode finger pitches are different from each other. Specifically, in regions where the electrode finger pitch is wide, the resonant frequency of the main mode is low. On the other hand, the width of the electrode fingers also affects the resonant frequency. Specifically, in regions where the electrode finger width is narrow, the resonant frequency of the main mode is high.

[0113] In IDT electrode 27C of this preferred embodiment, the width of the electrode fingers in wide-pitch region A1 is smaller than the average width M0 of the electrode fingers in IDT electrode 27C. The width of the electrode fingers in narrow-pitch region A2 is larger than the average width M0. This can suppress fluctuations in the main-mode resonant frequency of the acoustic wave device. This can also suppress a decrease in the Q value of the acoustic wave device.

[0114] In this embodiment, it is possible to suppress unwanted waves that are highly sensitive to the electrode finger pitch and electrode finger width, and also to prevent the Q value of the acoustic wave device from decreasing.

[0115] Additionally, in this embodiment, the adjacent chirp rate expressed by at least one of formulas (1) and (2) in the IDT electrode 27C is greater than 0°. The adjacent chirp rates expressed by both formulas (1) and (2) throughout the entire IDT electrode 27C are 0.6° or less. This reduces loss and improves power durability.

[0116] In the first embodiment shown in Fig. 2, the acoustic reflection portion in the elastic wave device 1 is a cavity 2a. This is also true for the second to seventh embodiments. The acoustic reflection portion may be an acoustic reflection film. An example of this is shown in the eighth embodiment.

[0117] FIG. 22 is a schematic front cross-sectional view of an elastic wave device according to the eighth preferred embodiment of the present invention.

[0118] This embodiment differs from the first embodiment in that the acoustic reflection portion is an acoustic reflection film 34. This embodiment also differs from the first embodiment in that the support member 33 is formed only from a support substrate. Except for the above points, the elastic wave device of this embodiment has the same configuration as the elastic wave device 1 of the first embodiment.

[0119] An acoustic reflection film 34 is provided on the surface of the support member 33. A piezoelectric layer 6 serving as a piezoelectric film is provided on the acoustic reflection film 34. The support member 33 and the piezoelectric film may be arranged such that at least a portion of the support member 33 and at least a portion of the piezoelectric film face each other with the acoustic reflection film 34 sandwiched therebetween.

[0120] The acoustic reflecting film 34 is a laminate of multiple acoustic impedance layers. Specifically, the acoustic reflecting film 34 has multiple low acoustic impedance layers and multiple high acoustic impedance layers. The low acoustic impedance layers are layers with a relatively low acoustic impedance. More specifically, the low acoustic impedance layers are layers with a lower acoustic impedance than the adjacent layers in the acoustic reflecting film 34. More specifically, the multiple low acoustic impedance layers in the acoustic reflecting film 34 are low acoustic impedance layer 37a, low acoustic impedance layer 37b, and low acoustic impedance layer 37c.

[0121] On the other hand, a high acoustic impedance layer is a layer with a relatively high acoustic impedance. More specifically, a high acoustic impedance layer is a layer with a higher acoustic impedance than the adjacent layers in the acoustic reflecting film 34. More specifically, the multiple high acoustic impedance layers in the acoustic reflecting film 34 are the high acoustic impedance layers 38a and 38b. The low acoustic impedance layers and the high acoustic impedance layers are alternately stacked. The low acoustic impedance layer 37a is the acoustic impedance layer located closest to the piezoelectric layer 6 in the acoustic reflecting film 34.

[0122] The acoustic reflection film 34 has three low acoustic impedance layers and two high acoustic impedance layers, although it is sufficient that the acoustic reflection film 34 has at least one low acoustic impedance layer and one high acoustic impedance layer.

[0123] The low acoustic impedance layer may be made of a dielectric material such as silicon oxide or a metal such as aluminum or titanium, while the high acoustic impedance layer may be made of a dielectric material such as aluminum nitride, silicon nitride, or hafnium oxide or a metal such as platinum or tungsten.

[0124] In this embodiment, the acoustic wave device is also configured to utilize thickness-shear bulk waves as the main mode. The electrode finger pitch in the IDT electrode 7 is varied, and the adjacent chirp rate expressed by equation (1) is greater than 0°, and the adjacent chirp rates expressed by both equations (1) and (2) are 0.6° or less. This reduces loss and improves power durability, similar to the first embodiment.

[0125] The configuration in this embodiment in which the acoustic reflecting portion is the acoustic reflecting film 34 can also be applied to configurations of the present invention other than this embodiment.

[0126] The first to eighth embodiments have been described above as examples in which the elastic wave device includes a single elastic wave resonator. However, an elastic wave device according to the present invention may also be an element including multiple elastic wave resonators. This example is shown in the ninth and tenth embodiments.

[0127] 23 is a schematic plan view of an elastic wave device according to a ninth preferred embodiment of the present invention, in which the IDT electrodes are shown as a rectangle with two diagonal lines added.

[0128] The acoustic wave device 40 is an element used as part of a filter device, a multiplexer, or the like. In the acoustic wave device 40, an IDT electrode 47A and an IDT electrode 47B are provided on a piezoelectric layer 6 serving as a piezoelectric film. This forms an acoustic wave resonator 41A including the IDT electrode 47A, and an acoustic wave resonator 41B including the IDT electrode 47B. Note that three or more IDT electrodes may be provided on the piezoelectric film. The acoustic wave device 40 may have three or more acoustic wave resonators, each including an IDT electrode.

[0129] In this embodiment, the IDT electrode 47A and the IDT electrode 47B are provided on the same piezoelectric film, that is, on the same piezoelectric layer 6. Note that the IDT electrode 47A and the IDT electrode 47B may be provided on separate piezoelectric films.

[0130] In plan view, an acoustic reflector is provided on the support member at a position that overlaps with the IDT electrode 47A and the IDT electrode 47B. The acoustic reflector may be a cavity or an acoustic reflecting film. The acoustic reflector that overlaps with the IDT electrode 47A in plan view and the acoustic reflector that overlaps with the IDT electrode 47B in plan view may be provided separately. Alternatively, the same acoustic reflector may overlap with the IDT electrode 47A and the IDT electrode 47B in plan view.

[0131] In each of IDT electrodes 47A and 47B, d / P0 is equal to or less than 0.5. In this manner, elastic wave resonators 41A and 41B are each configured to be able to use a bulk wave in thickness shear mode as the main mode.

[0132] In this embodiment, the electrode finger pitch varies in each of the IDT electrodes 47A and 47B. Meanwhile, the electrode finger width is constant in each of the IDT electrodes 47A and 47B. Specifically, in both the IDT electrodes 47A and 47B, the adjacent chirp rate expressed by equation (1) is greater than 0° and is equal to or less than 0.6°, and the adjacent chirp rate expressed by equation (2) is 0°.

[0133] Arctan[|P1-P2| / (P1+P2)]...Equation (1) Arctan[|Mmax-Mmin| / (P1+P2)]...Equation (2)

[0134] This reduces loss and improves power durability in elastic wave resonators 41A and 41B, thereby effectively reducing loss and improving power durability in elastic wave device 40 as a whole.

[0135] However, in the present invention, it is sufficient that d / P0 is 0.5 or less and at least one of the electrode finger pitch and the electrode finger width is changed in at least one IDT electrode. It is sufficient that at least one IDT electrode overlaps the acoustic reflection portion in a planar view. It is sufficient that at least a portion of at least one IDT electrode has an adjacent chirp rate expressed by at least one of formulas (1) and (2) greater than 0° and an adjacent chirp rate expressed by both formulas (1) and (2) equal to or less than 0.6°.

[0136] In the acoustic wave device 40, the sum of the chirp intensities expressed by at least one of formulas (3) and (4) for the IDT electrodes 47A and 47B is 5% or greater. More specifically, in this embodiment, the chirp intensities expressed by formula (3) are 5% or greater for both the IDT electrodes 47A and 47B. However, for example, the chirp intensities expressed by at least one of formulas (3) and (4) for the IDT electrodes 47A and 47B may each be less than 5%, and the sum of the chirp intensities may be 5% or greater.

[0137] |Pa_max-Pa_min| / P0...Equation (3) |Ma_max-Ma_min| / M0...Equation (4)

[0138] This allows suppression of unwanted waves in elastic wave resonators 41 A and 41 B. Therefore, unwanted waves can be effectively suppressed in elastic wave device 40 as a whole.

[0139] In addition, in at least one IDT electrode, the chirp intensity expressed by at least one of formulas (3) and (4) may be 5% or more.

[0140] In the elastic wave device 40, the IDT electrode 47A of the elastic wave resonator 41A and the IDT electrode 47B of the elastic wave resonator 41B have the same configuration as that of the third preferred embodiment shown in Fig. 11. However, the IDT electrodes 47A and 47B have different electrode finger pitch ranges.

[0141] 24A is a diagram illustrating the relationship between the position of the IDT electrode in the direction orthogonal to the electrode fingers and the electrode finger pitch in one acoustic wave resonator according to the ninth embodiment, and FIG. 24B is a diagram illustrating the relationship between the position of the IDT electrode in the direction orthogonal to the electrode fingers and the electrode finger pitch in the other acoustic wave resonator according to the ninth embodiment.

[0142] 24(a) shows the range of electrode finger pitches in the IDT electrode 47A of the acoustic wave resonator 41A. 24(b) shows the range of electrode finger pitches in the IDT electrode 47B of the acoustic wave resonator 41B. The dashed lines px in FIGS. 24(a) and 24(b) indicate the average value of Pa_max in the IDT electrode 47A and Pa_min in the IDT electrode 47B. As shown in FIGS. 24(a) and 24(b), Pa_max in the IDT electrode 47B is smaller than Pa_min in the IDT electrode 47A.

[0143] As shown in FIG. 23 , elastic wave resonators 41A and 41B are connected in parallel. If the electrode finger pitches of the IDT electrodes of the elastic wave resonators connected in parallel are the same, the frequencies at which unwanted waves are generated in each elastic wave resonator may also be the same. In this case, the unwanted waves will reinforce each other. In contrast, in elastic wave device 40, Pa_max of one of IDT electrodes 47A and 47B is smaller than Pa_min of the other. This prevents the unwanted waves from reinforce each other. Therefore, unwanted waves can be suppressed throughout elastic wave device 40.

[0144] The elastic wave device of the present invention may have at least one of the following configurations: a configuration in which the Pa_max of one of the two IDT electrodes is smaller than the Pa_min of the other; and a configuration in which the Ma_max of one of the two IDT electrodes is smaller than the Ma_min of the other.

[0145] A tenth embodiment will be described below, illustrating an example of a configuration in which Ma_max of one of two IDT electrodes is smaller than Ma_min of the other. The elastic wave device of the tenth embodiment has the same configuration as elastic wave device 40 of the ninth embodiment, except that the electrode finger pitch is constant in each of the two IDT electrodes and the electrode finger widths vary in each of the two IDT electrodes. Therefore, the tenth embodiment will be described using the same reference numerals and symbols as those used in the description of the ninth embodiment.

[0146] In the tenth preferred embodiment, the adjacent chirp rate expressed by equation (2) is greater than 0° and equal to or less than 0.6° for both the IDT electrode 47A of the acoustic wave resonator 41A and the IDT electrode 47B of the acoustic wave resonator 41B. Meanwhile, the adjacent chirp rate expressed by equation (1) is 0°. In the tenth preferred embodiment, as in the ninth preferred embodiment, the acoustic wave device as a whole can effectively reduce loss and effectively increase power durability.

[0147] 23 , elastic wave resonators 41A and 41B are connected in parallel to each other. In the tenth embodiment, the width ranges of the electrode fingers of an IDT electrode 47A of elastic wave resonator 41A and an IDT electrode 47B of elastic wave resonator 41B are different from each other.

[0148] 25(a) is a diagram showing the relationship between the position of the IDT electrode in the direction orthogonal to the electrode fingers and the width of the electrode fingers in one acoustic wave resonator according to the tenth embodiment, and Fig. 25(b) is a diagram showing the relationship between the position of the IDT electrode in the direction orthogonal to the electrode fingers and the width of the electrode fingers in the other acoustic wave resonator according to the tenth embodiment.

[0149] FIG. 25( a ) shows the range of electrode finger widths in the IDT electrode 47A of the acoustic wave resonator 41A. FIG. 25( b ) shows the range of electrode finger widths in the IDT electrode 47B of the acoustic wave resonator 41B. The dashed line mx in FIGS. 25( a ) and 25( b ) indicates the average value of Ma_max in the IDT electrode 47A and Ma_min in the IDT electrode 47B. As shown in FIGS. 25( a ) and 25( b ), Ma_max in the IDT electrode 47B is smaller than Ma_min in the IDT electrode 47A. Thus, in the tenth embodiment, as in the ninth embodiment, it is possible to suppress the reinforcement of unwanted waves in the acoustic wave resonators 41A and 41B. Therefore, it is possible to suppress unwanted waves throughout the entire acoustic wave device.

[0150] As shown in the first to tenth embodiments, an acoustic wave device according to the present invention only needs to have at least one IDT electrode provided on the piezoelectric film. Specifically, the first to tenth embodiments show examples in which one or two IDT electrodes are provided on the piezoelectric film.

[0151] In addition, it is sufficient that d / P0≦0.5 is satisfied in at least one IDT electrode. It is sufficient that the adjacent chirp rate expressed by at least one of formulas (1) and (2) is greater than 0° in at least a portion of at least one IDT electrode for which d / P0≦0.5 is satisfied. It is sufficient that the adjacent chirp rate expressed by both formulas (1) and (2) is 0.6° or less in the entire IDT electrode.

[0152] Arctan[|P1-P2| / (P1+P2)]...Equation (1) Arctan[|Mmax-Mmin| / (P1+P2)]...Equation (2)

[0153] An acoustic wave device according to a preferred embodiment of the present invention can be used, for example, in a filter device, as will be described in the eleventh preferred embodiment.

[0154] FIG. 26 is a circuit diagram of a filter device according to an eleventh embodiment of the present invention.

[0155] The filter device 50 is a ladder-type filter. The filter device 50 has a first signal terminal 52, a second signal terminal 53, and a plurality of acoustic wave resonators. In this embodiment, the second signal terminal 53 is an antenna terminal. The antenna terminal is connected to an antenna. Note that the second signal terminal 53 does not necessarily have to be an antenna terminal. The first signal terminal 52 and the second signal terminal 53 may be configured as electrode pads or as wiring.

[0156] Each of the plurality of elastic wave resonators in this embodiment is an elastic wave device according to the present invention as a single elastic wave resonator. Specifically, the plurality of elastic wave resonators in this embodiment is, for example, any of the elastic wave devices according to the first to eighth embodiments. Note that it is sufficient that at least one elastic wave resonator has at least one IDT electrode.

[0157] Specifically, the IDT electrode satisfies d / P0≦0.5, and at least a portion of the IDT electrode has an adjacent chirp rate greater than 0°, as expressed by at least one of formulas (1) and (2). The entire IDT electrode has an adjacent chirp rate less than or equal to 0.6°, as expressed by both formulas (1) and (2). The IDT electrode is, for example, the IDT electrode according to any one of the first to eighth embodiments.

[0158] The plurality of acoustic wave resonators of the filter device 50 include a plurality of series arm resonators and a plurality of parallel arm resonators. Specifically, the plurality of series arm resonators in this embodiment are a series arm resonator S1, a series arm resonator S2, and a series arm resonator S3. The series arm resonators S1, S2, and S3 are connected in series with each other between a first signal terminal 52 and a second signal terminal 53. In terms of the circuit configuration, the series arm resonator S1, the series arm resonator S2, and the series arm resonator S3 are arranged in this order from the first signal terminal 52 side.

[0159] Specifically, the parallel arm resonators of this embodiment are a parallel arm resonator Z1 and a parallel arm resonator Z2. The parallel arm resonator Z1 is connected between the connection point between the series arm resonators S1 and S2 and ground potential. The parallel arm resonator Z2 is connected between the connection point between the series arm resonators S2 and S3 and ground potential.

[0160] It should be noted that the circuit configuration of the filter device 50 is not limited to the above. When the filter device 50 is a ladder-type filter, it is sufficient that the filter device 50 has at least one series arm resonator and at least one parallel arm resonator.

[0161] Alternatively, the filter device according to the present invention may include a longitudinally coupled resonator type acoustic wave filter. In this case, the filter device may include at least one series arm resonator and at least one parallel arm resonator. In this specification, both acoustic wave resonators and longitudinally coupled resonator type acoustic wave filters are included in the term "resonators." The filter device according to the present invention may include a plurality of resonators, including a longitudinally coupled resonator type acoustic wave filter. In the filter device according to the present invention, at least one resonator may be either a series arm resonator or a parallel arm resonator, and may be the acoustic wave device according to the present invention.

[0162] The filter device 50 uses an elastic wave device according to the present invention as an elastic wave resonator. This reduces loss in the elastic wave resonator and improves power handling. This reduces the insertion loss of the filter device 50, and improves the power handling capability of the entire filter device 50.

[0163] Note that a filter device according to the present invention may include an acoustic wave device that is an element used as part of a filter device, such as in the ninth or tenth embodiment. For example, a filter device 50A according to a modification of the eleventh embodiment shown in Fig. 27 is a ladder filter that uses the acoustic wave device of the ninth embodiment. The circuit configuration of this modification is similar to the circuit configuration of the eleventh embodiment shown in Fig. 26, except that the parallel arm resonator Z1 is replaced with parallel arm resonators Z11a and Z11b.

[0164] The parallel arm resonators Z11a and Z11b are connected in parallel between the connection point between the series arm resonators S1 and S2 and ground potential. The parallel arm resonators Z11a and Z11b are two elastic wave resonators in the elastic wave device 40 according to the ninth preferred embodiment.

[0165] The parallel arm resonator Z11a and the parallel arm resonator Z11b may be the two elastic wave resonators in the elastic wave device according to the tenth preferred embodiment. Alternatively, for example, the two elastic wave resonators in the ninth or tenth preferred embodiment may be two series arm resonators connected in parallel to each other.

[0166] In this modification, similarly to the eleventh embodiment, the loss in the acoustic wave resonator can be reduced and the power handling capability can be increased, thereby reducing the insertion loss of the filter device 50A and increasing the power handling capability of the entire filter device 50A.

[0167] A preferred configuration of the present invention will be described below with reference to Fig. 1. However, the following preferred configuration can also be applied to configurations of the present invention other than the first embodiment.

[0168] In the first embodiment, when the thickness of the piezoelectric film is d and the average electrode finger pitch is P, d / P is 0.5 or less. Preferably, d / P is 0.24 or less. This allows thickness-shear mode bulk waves to be more effectively excited and enables the bandwidth fraction of the elastic wave resonator to be sufficiently increased.

[0169] FIG. 28 is a graph showing the relationship between d / P0 and the fractional bandwidth of an elastic wave resonator.

[0170] As is clear from FIG. 28, when d / P0 > 0.5, the fractional bandwidth is less than 5%. In contrast, when d / P0 ≦ 0.5, the fractional bandwidth can be made 5% or more. This allows the electromechanical coupling coefficient of the thickness-shear mode bulk wave to be increased. When d / P0 ≦ 0.24, the fractional bandwidth can be made 7% or more. This allows the electromechanical coupling coefficient of the thickness-shear mode bulk wave to be effectively increased. For these reasons, in the present invention, it is preferable that d / P0 ≦ 0.24 be satisfied for at least one IDT electrode.

[0171] When the metallization ratio of the electrode fingers to the excitation region C is MR, it is preferable to satisfy MR≦1.75(d / P0)+0.075. In this case, the value of the fractional bandwidth of the acoustic wave resonator does not become too large, and the occurrence of spurious signals between the resonant frequency and the antiresonant frequency can be suppressed. Details of this are described below.

[0172] In this specification, the metallization ratio MR of the electrode fingers to the excitation region C is the ratio of the portion of the piezoelectric layer 6 that is covered with the metal constituting the electrode fingers to the excitation region C in a plan view. Specifically, the metallization ratio MR is the ratio of the area of ​​the first electrode fingers 18 and the second electrode fingers 19 in the excitation region C to the area of ​​the excitation region C in a plan view. When the width of the electrode fingers located in the excitation region C is constant, the metallization ratio MR can also be calculated by dividing the sum of the widths of the electrode fingers located in the excitation region C by the dimension of the excitation region C in the direction perpendicular to the electrode fingers. The width of the electrode fingers is the dimension of the electrode fingers in the direction perpendicular to the electrode fingers.

[0173] Fig. 29 is a diagram showing the relationship between the relative bandwidth and the normalized magnitude of spurious in an elastic wave resonator. Fig. 29 shows the results of measuring the amount of phase rotation of spurious every time the relative bandwidth is changed by changing the thickness of the piezoelectric layer and the dimensions of the electrode fingers. Note that the normalized magnitude of spurious in Fig. 29 is specifically a value in which the amount of phase rotation of the spurious impedance is normalized by 180°. The results shown in Fig. 29 are for a Z-cut LiNbO ３ Although this is the result when a piezoelectric layer made of this material was used, the same tendency is observed when a piezoelectric layer having another cut angle is used.

[0174] In the region surrounded by ellipse D in Figure 29, the normalized magnitude of the spurious response between the resonant frequency and the anti-resonant frequency is 1.0. If the bandwidth fraction of the elastic wave resonator exceeds 17%, the normalized magnitude of the spurious response may be 1.0 or more. For this reason, it is preferable that the bandwidth fraction be 17% or less. This makes it possible to suppress the spurious response between the resonant frequency and the anti-resonant frequency.

[0175] 30 is a diagram showing the relationship between d / P0, metallization ratio MR, and fractional bandwidth, in which the results of calculating fractional bandwidth for different d / P0 and metallization ratio MR are shown.

[0176] In Figure 30, the hatched area is the area where the fractional bandwidth is 17% or less. The boundary between this hatched area and the non-hatched area is roughly represented by dashed line G. Dashed line G is represented by MR = 1.75(d / P0) + 0.075. It is preferable that MR ≤ 1.75(d / P0) + 0.075. In this case, it is easy to keep the fractional bandwidth at 17% or less.

[0177] On the other hand, the dashed-dotted line G1 in Figure 30 indicates the boundary where the slope of the change in metallization ratio MR with respect to changes in d / P0 is the same as that of the dashed line G, and the bandwidth ratio is 17% or less over the entire range. The dashed-dotted line G1 is represented by MR = 1.75(d / P0) + 0.05. It is more preferable that MR ≤ 1.75(d / P0) + 0.05. In this case, the bandwidth ratio can be more reliably kept to 17% or less. For these reasons, in the present invention, in the portion where at least one IDT electrode is provided, it is preferable that MR ≤ 1.75(d / P0) + 0.075, and more preferably that MR ≤ 1.75(d / P0) + 0.05.

[0178] FIG. 31 shows the LiNbO ３ 31 is a diagram showing a map of fractional bandwidths with respect to Euler angles (0°, θ, ψ) of the frequency domain. The hatched area in FIG. 31 is a region where a fractional bandwidth of at least 5% or more can be obtained, and the range of this region can be approximated to the ranges expressed by the following formulas (5), (6), and (7).

[0179] (0°±10°, 0° to 20°, any ψ) ... Equation (5) (0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ２ / 900) １／２ ) or (0°±10°, 20° to 80°, [180°-60° (1-(θ-50) ２ / 900) １／２ ]~180°) ...Formula (6) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２ ] to 180°, any ψ) ...Equation (7)

[0180] It is preferable that the Euler angles (φ, θ, ψ) of the lithium niobate constituting the piezoelectric layer are within the range of the above formula (5), formula (6), or formula (7). This allows the relative bandwidth of the elastic wave resonator to be sufficiently wide. The same applies when the piezoelectric layer is made of lithium tantalate.

[0181] The following describes examples of acoustic wave devices and filter devices according to the present invention.

[0182] <1> A piezoelectric transducer comprising: a support member; a piezoelectric film provided on the support member and including a piezoelectric layer; and at least one IDT electrode provided on the piezoelectric film and having a plurality of electrode fingers, wherein an acoustic reflector is provided on the support member at a position overlapping with at least one of the IDT electrodes in a plan view; when the thickness of the piezoelectric film is d and the average value of the electrode finger pitch in the IDT electrode is P0, in the at least one IDT electrode, d / P0 is 0.5 or less; and in the at least one IDT electrode, An acoustic wave device in which at least one of the finger widths varies, and in three consecutive electrode fingers, when one electrode finger pitch is P1 and the other electrode finger pitch is P2, and the widest width of the three consecutive electrode fingers is Mmax and the narrowest width is Mmin, the adjacent chirp rate expressed by at least one of the following equations (1) and (2) is greater than 0° in at least a portion of the at least one IDT electrode, and the adjacent chirp rates expressed by both of the following equations (1) and (2) are 0.6° or less in the entire IDT electrode: Arctan[|P1-P2| / (P1+P2)] ...equation (1) Arctan[|Mmax-Mmin| / (P1+P2)] ...equation (2)

[0183] <2> The acoustic wave device according to <1>, wherein, in the entire IDT electrode, the longest electrode finger pitch is Pa_max, the shortest electrode finger pitch is Pa_min, the widest width of the plurality of electrode fingers in the entire IDT electrode is Ma_max, the narrowest width is Ma_min, and an average value of the widths of the plurality of electrode fingers in the IDT electrode is M0, the chirp intensity expressed by at least one of the following formulas (3) and (4) is 5% or more: |Pa_max-Pa_min| / P0 ... formula (3) |Ma_max-Ma_min| / M0 ... formula (4)

[0184] <3> The acoustic wave device according to <2>, wherein the chirp intensity expressed by at least one of the formulas (3) and (4) in the at least one IDT electrode is 10% or more.

[0185] <4> The elastic wave device according to any one of <1> to <3>, wherein in the at least one IDT electrode, at least one of the electrode finger pitch and the electrode finger width increases toward the center of the IDT electrode.

[0186] <5> The elastic wave device according to any one of <1> to <3>, wherein in the at least one IDT electrode, at least one of the electrode finger pitch and the electrode finger width decreases toward the center of the IDT electrode.

[0187] <6> An elastic wave device according to any one of <1> to <3>, wherein, when a direction perpendicular to the direction in which the plurality of electrode fingers extend is defined as an electrode finger perpendicular direction, at least one of the electrode finger pitch value and the electrode finger width value in the at least one IDT electrode decreases from one end of the IDT electrode to the other end in the electrode finger perpendicular direction.

[0188] <7> The elastic wave device according to any one of <1> to <6>, wherein the at least one IDT electrode includes an IDT electrode in which the electrode finger pitch and the width of the electrode fingers vary, and in the IDT electrode in which the electrode finger pitch and the width of the electrode fingers vary, the width of the electrode fingers in a region where the electrode finger pitch is larger than the average electrode finger pitch P0 is smaller than the average width of the multiple electrode fingers in the IDT electrode.

[0189] <8> The elastic wave device according to any one of <1> to <7>, wherein, when a direction perpendicular to the direction in which the plurality of electrode fingers extend is defined as an electrode finger orthogonal direction, a region in which adjacent electrode fingers overlap each other in the electrode finger orthogonal direction and a region between the centers of adjacent electrode fingers is defined as an excitation region, and when a metallization ratio of the electrode fingers to the excitation region is defined as MR, a relationship of MR≦1.75(d / P0)+0.075 is satisfied in a portion in which the at least one IDT electrode is provided.

[0190] <9> An elastic wave device described in any one of <1> to <8>, wherein the acoustic reflection portion is a hollow portion, and the support member and the piezoelectric film are arranged so that a portion of the support member and a portion of the piezoelectric film face each other across the hollow portion.

[0191] <10> An elastic wave device described in any one of <1> to <8>, wherein the acoustic reflection portion is an acoustic reflection film including a high acoustic impedance layer having a relatively high acoustic impedance and a low acoustic impedance layer having a relatively low acoustic impedance, and the support member and the piezoelectric film are arranged so that at least a portion of the support member and at least a portion of the piezoelectric film face each other with the acoustic reflection film in between.

[0192] <11> The acoustic wave device according to any one of <1> to <10>, wherein the piezoelectric layer is made of lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (5), formula (6), or formula (7): (0°±10°, 0° to 20°, any ψ) ... formula (5) (0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ２ / 900) １／２ ) or (0°±10°, 20° to 80°, [180°-60° (1-(θ-50) ２ / 900) １／２ ]~180°) ...Formula (6) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２ ] to 180°, any ψ) ...Equation (7)

[0193] <12> The elastic wave device according to any one of <1> to <11>, including at least two IDT electrodes, wherein the acoustic reflector is provided on the support member at a position overlapping with the two IDT electrodes in a plan view, wherein d / P0 is 0.5 or less in each of the two IDT electrodes, and at least one of the electrode finger pitch and the electrode finger width is varied, wherein the longest electrode finger pitch throughout the IDT electrodes is Pa_max and the shortest electrode finger pitch is Pa_min, the widest width of the plurality of electrode fingers throughout the IDT electrode is Ma_max and the narrowest width is Ma_min, and the average value of the widths of the plurality of electrode fingers in the IDT electrode is M0, the sum of the chirp intensities expressed by at least one of the following formulas (3) and (4) in the two IDT electrodes is 5% or more, and wherein two elastic wave resonators each including the two IDT electrodes are configured, and the two elastic wave resonators are connected in parallel. |Pa_max-Pa_min| / P0...Equation (3) |Ma_max-Ma_min| / M0...Equation (4)

[0194] <13> The elastic wave device according to <12>, having at least one of the following configurations: a configuration in which the Pa_max of one of the two IDT electrodes is smaller than the Pa_min of the other; and a configuration in which the Ma_max of one of the two IDT electrodes is smaller than the Ma_min of the other.

[0195] <14> The acoustic wave device according to any one of <1> to <11>, wherein d / P0 is 0.24 or less in the at least one IDT electrode.

[0196] <15> The acoustic wave device according to <12> or <13>, wherein d / P0 is 0.24 or less in the at least one IDT electrode.

[0197] <16> A filter device comprising a plurality of resonators, the plurality of resonators including at least one of at least one series arm resonator and at least one parallel arm resonator, and at least one of the plurality of resonators being the elastic wave device described in any one of <1> to <11> or <14>.

[0198] <17> A filter device comprising the elastic wave device according to any one of <12>, <13>, and <15>, and at least one resonator other than the two elastic wave resonators, wherein the two elastic wave resonators are either series arm resonators connected in parallel to each other or parallel arm resonators connected in parallel to each other.

[0199] REFERENCE SIGNS LIST 1...acoustic wave device 2...piezoelectric substrate 2a...cavity 3...support member 4...support substrate 5...insulating layer 6...piezoelectric layer 6a, 6b...first and second principal surfaces 7, 7A, 7B...IDT electrodes 16, 17...first and second bus bars 18, 19...first and second electrode fingers 21...acoustic wave device 27, 27A to 27C...IDT electrodes 33...support member 34...acoustic reflecting film 37a to 37c...low acoustic impedance layers 38a, 38b...high acoustic impedance layers 40...acoustic wave device 41A, 41B...acoustic wave resonators 47A, 47B...IDT electrodes 50, 50A...filter device 52, 53...first and second signal terminals A1...wide pitch region A2...narrow pitch region C...excitation region F...crossing region S1 to S3...series arm resonators Z1, Z2, Z11a, Z11b...parallel arm resonators

Claims

1. A piezoelectric transducer comprising: a support member; a piezoelectric film provided on the support member and including a piezoelectric layer; and at least one IDT electrode provided on the piezoelectric film and having a plurality of electrode fingers, wherein an acoustic reflecting portion is provided on the support member at a position overlapping with at least one of the IDT electrodes in a plan view; when the thickness of the piezoelectric film is d and the average value of the electrode finger pitch in the IDT electrode is P0, d / P0 is 0.5 or less in the at least one IDT electrode; and at least one of the electrode finger pitch and the width of the electrode fingers is varied in the at least one IDT electrode; An acoustic wave device, wherein, in three consecutive electrode fingers, one electrode finger pitch is P1, the other electrode finger pitch is P2, the widest width of the three consecutive electrode fingers is Mmax, and the narrowest width of the three consecutive electrode fingers is Mmin, the adjacent chirp rate expressed by at least one of the following formulas (1) and (2) is greater than 0° in at least a part of the at least one IDT electrode, and the adjacent chirp rate expressed by both of the following formulas (1) and (2) is 0.6° or less in the entire IDT electrode: Arctan[|P1-P2| / (P1+P2)] ... formula (1) Arctan[|Mmax-Mmin| / (P1+P2)] ... formula (2) 2. The acoustic wave device according to claim 1, wherein, in the entire IDT electrode, the longest electrode finger pitch is Pa_max, the shortest electrode finger pitch is Pa_min, the widest width of the plurality of electrode fingers in the entire IDT electrode is Ma_max, the narrowest width is Ma_min, and the average width of the plurality of electrode fingers in the IDT electrode is M0, the chirp intensity expressed by at least one of the following formulas (3) and (4) is 5% or greater: |Pa_max-Pa_min| / P0 ... formula (3) |Ma_max-Ma_min| / M0 ... formula (4) 3. The acoustic wave device according to claim 2, wherein the chirp intensity expressed by at least one of the formulas (3) and (4) in the at least one IDT electrode is 10% or more.

4. An elastic wave device according to any one of claims 1 to 3, wherein in at least one of the IDT electrodes, at least one of the electrode finger pitch and the electrode finger width increases toward the center of the IDT electrode.

5. An elastic wave device according to any one of claims 1 to 3, wherein in at least one of the IDT electrodes, at least one of the electrode finger pitch and the electrode finger width decreases toward the center of the IDT electrode.

6. An elastic wave device according to any one of claims 1 to 3, wherein, when a direction perpendicular to the direction in which the plurality of electrode fingers extend is defined as the electrode finger perpendicular direction, at least one of the electrode finger pitch value and the electrode finger width value in at least one IDT electrode decreases from one end of the IDT electrode to the other end in the electrode finger perpendicular direction.

7. The elastic wave device according to any one of claims 1 to 6, wherein the at least one IDT electrode includes an IDT electrode in which the electrode finger pitch and the width of the electrode fingers vary, and in the IDT electrode in which the electrode finger pitch and the width of the electrode fingers vary, the width of the electrode fingers in a region where the electrode finger pitch is larger than the average electrode finger pitch P0 is smaller than the average width of the multiple electrode fingers in the IDT electrode.

8. The elastic wave device according to any one of claims 1 to 7, wherein, when a direction perpendicular to the direction in which the plurality of electrode fingers extend is defined as an electrode finger perpendicular direction, a region where adjacent electrode fingers overlap in the electrode finger perpendicular direction and a region between the centers of adjacent electrode fingers is defined as an excitation region, and when a metallization ratio of the electrode fingers to the excitation region is defined as MR, a relationship of MR≦1.75(d / P0)+0.075 is satisfied in a portion where the at least one IDT electrode is provided.

9. An elastic wave device according to any one of claims 1 to 8, wherein the acoustic reflection portion is a hollow portion, and the support member and the piezoelectric film are arranged so that a portion of the support member and a portion of the piezoelectric film face each other across the hollow portion.

10. An elastic wave device according to any one of claims 1 to 8, wherein the acoustic reflection portion is an acoustic reflection film including a high acoustic impedance layer with a relatively high acoustic impedance and a low acoustic impedance layer with a relatively low acoustic impedance, and the support member and the piezoelectric film are arranged so that at least a portion of the support member and at least a portion of the piezoelectric film face each other with the acoustic reflection film in between.

11. The acoustic wave device according to any one of claims 1 to 10, wherein the piezoelectric layer is made of lithium niobate or lithium tantalate, and the Euler angles (φ, θ, ψ) of the lithium niobate or lithium tantalate constituting the piezoelectric layer are within the range of the following formula (5), formula (6), or formula (7): (0°±10°, 0° to 20°, any ψ) ... formula (5) (0°±10°, 20° to 80°, 0° to 60° (1-(θ-50) ２ / 900) １／２ ) or (0°±10°, 20° to 80°, [180°-60° (1-(θ-50) ２ / 900) １／２ ]~180°) ...Formula (6) (0°±10°, [180°-30°(1-(ψ-90) ２ / 8100) １／２ ] to 180°, any ψ) ...Equation (7) 12. The elastic wave device according to any one of claims 1 to 11, comprising at least two of the IDT electrodes, wherein the acoustic reflector is provided on the support member at a position overlapping the two IDT electrodes in a planar view, wherein d / P0 is 0.5 or less in each of the two IDT electrodes, and at least one of the electrode finger pitch and the electrode finger width is varied, wherein the longest electrode finger pitch throughout the IDT electrode is Pa_max and the shortest electrode finger pitch is Pa_min, the widest width of the multiple electrode fingers throughout the IDT electrode is Ma_max and the narrowest width is Ma_min, and the average width of the multiple electrode fingers in the IDT electrode is M0, the total chirp intensity expressed by at least one of the following equations (3) and (4) in the two IDT electrodes is 5% or more, and wherein two elastic wave resonators each including the two IDT electrodes are configured, and the two elastic wave resonators are connected in parallel. |Pa_max-Pa_min| / P0...Equation (3) |Ma_max-Ma_min| / M0...Equation (4) 13. The elastic wave device according to claim 12, having at least one of a configuration in which the Pa_max of one of the two IDT electrodes is smaller than the Pa_min of the other, and a configuration in which the Ma_max of one of the two IDT electrodes is smaller than the Ma_min of the other.

14. The acoustic wave device according to claim 1, wherein d / P0 is 0.24 or less in the at least one IDT electrode.

15. The acoustic wave device according to claim 12, wherein d / P0 is 0.24 or less in the at least one IDT electrode.

16. A filter device comprising a plurality of resonators, the plurality of resonators including at least one series arm resonator and at least one parallel arm resonator, and at least one of the plurality of resonators being the elastic wave device recited in any one of claims 1 to 11 or 14.

17. A filter device comprising: the elastic wave device according to any one of claims 12, 13, and 15; and at least one resonator other than the two elastic wave resonators, wherein the two elastic wave resonators are either series arm resonators connected in parallel to each other or parallel arm resonators connected in parallel to each other.

Images