Elastic wave device and ladder filter having the same

Abstract

An elastic wave device (100) includes a substrate (105) having a piezoelectric layer (110), a first resonator (101) and a second resonator (102) disposed on the substrate, and a common reflector (REF12). The second resonator is disposed on the substrate adjacent to the first resonator and has a different frequency characteristic from the first resonator. The common reflector is disposed on the substrate between the first resonator and the second resonator and functions as a reflector for both the first resonator and the second resonator. The first resonator includes a first IDT electrode (IDT1) having electrode fingers formed at a first pitch. The second resonator includes a second IDT electrode (IDT2) having electrode fingers formed at a second pitch. A lower limit frequency of a stop band of the common reflector is between a lower limit frequency of a stop band of the first resonator and a lower limit frequency of a stop band of the second resonator. An upper limit frequency of the stop band of the common reflector is between an upper limit frequency of the stop band of the first resonator and an upper limit frequency of the stop band of the second resonator.

Description

Technical Field

[0001] This disclosure relates to elastic wave devices and trapezoidal filters having the elastic wave devices, and more specifically, to techniques for miniaturizing elastic wave devices. Background Technology

[0002] Japanese Patent Application Publication No. 10-303691 (Patent Document 1) discloses a filter device composed of multiple surface acoustic wave (SAW) resonators. Typically, in such a filter device, reflectors are arranged on both sides of the interdigital transducer (IDT) electrodes forming the SAW resonators to suppress signal leakage from the resonators.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-303691

[0006] Patent Document 2: Japanese Patent Application Publication No. 2002-176335 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The aforementioned filter devices using surface acoustic wave resonators are sometimes used in portable terminals such as mobile phones or smartphones. In portable terminals, the demand for miniaturization and thinness remains high, and consequently, devices constituting these portable terminals, such as filter devices, also require further miniaturization and thinning.

[0009] To address this problem, for example, Japanese Patent Application Publication No. 2002-176335 (Patent Document 2) proposes a structure in which adjacent surface acoustic wave (SAW) resonators share a reflector disposed between the IDT electrodes, thereby achieving miniaturization of the overall elastic wave device. However, the frequency characteristics of adjacent SAW resonators vary depending on the device's structure; therefore, simply sharing a reflector may actually degrade the overall frequency characteristics of the device, potentially failing to achieve the desired characteristics.

[0010] The present invention was made to solve the above-mentioned problems, and its purpose is to suppress the decline of the frequency characteristics of the elastic wave device formed by multiple resonators and to achieve miniaturization.

[0011] means for solving problems

[0012] The elastic wave device of the first aspect of this disclosure includes: a substrate having a piezoelectric layer; a first resonator and a second resonator disposed on the substrate; and a common reflector. The second resonator is disposed adjacent to the first resonator on the substrate and has different frequency characteristics from the first resonator. The common reflector is disposed on the substrate between the first and second resonators, functioning as a reflector for both the first and second resonators. The first resonator includes a first IDT electrode with electrode fingers formed at a first spacing. The second resonator includes a second IDT electrode with electrode fingers formed at a second spacing. The lower stopband frequency of the common reflector is the same as, or between, the lower stopband frequencies of the first and second resonators. The upper stopband frequency of the common reflector is the same as, or between, the upper stopband frequencies of the first and second resonators.

[0013] The elastic wave device of the second aspect of this disclosure includes: a substrate having a piezoelectric layer; a first resonator and a second resonator disposed on the substrate; and a common reflector. The second resonator is disposed adjacent to the first resonator on the substrate and has a different frequency response than the first resonator. The common reflector is disposed on the substrate between the first and second resonators, functioning as a reflector for both the first and second resonators. The first resonator includes a first IDT electrode with electrode fingers formed at a first spacing. The second resonator includes a second IDT electrode with electrode fingers formed at a second spacing. Regarding the common reflector, the first resonator, and the second resonator, when the value obtained by multiplying the spacing of the electrode fingers, the duty cycle of the electrode fingers, and the thickness of the electrode fingers are respectively set as a first value, a second value, and a third value, the first value is the same as the second and third values, or is between the second and third values.

[0014] Invention Effects

[0015] According to the elastic wave device disclosed herein, a common reflector is configured between two elastic wave resonators (a first resonator and a second resonator), each including an IDT electrode, to function as a reflector for both. Furthermore, the lower stopband frequency of this common reflector is set between the lower stopband frequencies of the two resonators, and the upper stopband frequency is set between the upper stopband frequencies of the two resonators. By employing this structure, signals from the IDT of either resonator are reflected by the common reflector. Therefore, it is possible to suppress the degradation of the frequency characteristics of the elastic wave device and achieve miniaturization. Attached Figure Description

[0016] Figure 1This is the circuit structure of the filter device formed by the elastic wave device of Embodiment 1.

[0017] Figure 2 This is a top view used to illustrate the basic structure of the elastic wave device of Embodiment 1.

[0018] Figure 3 This is a cross-sectional view of the elastic wave device according to Embodiment 1.

[0019] Figure 4 This is a top view of a comparative example elastic wave device.

[0020] Figure 5 This is a top view of the filter device of the elastic wave device in Embodiment 1 and the comparative example.

[0021] Figure 6 It is used for explanation Figure 5 A diagram showing the detailed structure of part of region RG1 in (b).

[0022] Figure 7 It is used for explanation Figure 5 A diagram showing the detailed structure of part of region RG2 in (b).

[0023] Figure 8 This is a graph used to illustrate the frequency characteristics of the elastic wave device in the comparative example.

[0024] Figure 9 This is a diagram used to illustrate the frequency characteristics of the elastic wave device in Embodiment 1.

[0025] Figure 10 This is a diagram illustrating an example of the specifications of the elastic wave device according to Embodiment 1.

[0026] Figure 11 This is a top view of the elastic wave device in Modified Example 1.

[0027] Figure 12 This is a top view of the elastic wave device in Modified Example 2.

[0028] Figure 13 This is a cross-sectional view of the elastic wave device according to Embodiment 2.

[0029] Figure 14 This is a diagram illustrating an example of the specifications of the elastic wave device according to Embodiment 2.

[0030] Figure 15 This is a cross-sectional view of the elastic wave device according to Embodiment 3.

[0031] Figure 16 This is a diagram illustrating an example of the specifications of the elastic wave device according to Embodiment 3.

[0032] Figure 17This is a cross-sectional view of the elastic wave device according to Embodiment 4.

[0033] Figure 18 The diagram shows other examples of the configuration of the dielectric layer. Detailed Implementation

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the same or equivalent parts in the drawings are labeled with the same reference numerals, and their descriptions will not be repeated.

[0035] [Implementation Method 1]

[0036] (Structure of the filter device)

[0037] Figure 1 This is a diagram showing the circuit structure of the filter device 10 formed by the elastic wave device of Embodiment 1. The filter device 10 is, for example, a filter device for the transmitting side circuit of a communication device, and is a ladder filter connected between the transmitting terminal TX and the antenna terminal ANT. The filter device 10 filters the signal received by the transmitting terminal TX and outputs it from the antenna terminal ANT.

[0038] The filter device 10 includes series arm resonators S1-S5 and parallel arm resonators P1-P4 connected in series between the transmitting terminal TX and the antenna terminal ANT. Each of the series arm resonators S1-S5 and the parallel arm resonators P1-P4 is configured to include at least one elastic wave resonator. Figure 1 In the example, each of the series arm resonators S1 and S5 and the parallel arm resonators P1 to P4 includes one elastic wave resonator, and each of the series arm resonators S2 to S4 includes two elastic wave resonators. Series arm resonator S2 is configured to include elastic wave resonators S21 and S22 connected in series. Series arm resonator S3 is configured to include elastic wave resonators S31 and S32 connected in series. Series arm resonator S4 is configured to include elastic wave resonators S41 and S42 connected in series. It should be noted that the number of elastic wave resonators included in each resonator is not limited to these numbers and should be appropriately selected to match the characteristics of the filter device. Surface acoustic wave (SAW) resonators can be used as elastic wave resonators.

[0039] One end of the parallel arm resonator P1 is connected to the connection point between the series arm resonators S1 and S2, and the other end is connected to the ground potential. One end of the parallel arm resonator P2 is connected to the connection point between the series arm resonators S2 and S3, and the other end is connected to the ground potential. One end of the parallel arm resonator P3 is connected to the connection point between the series arm resonators S3 and S4, and the other end is connected to the ground potential. One end of the parallel arm resonator P4 is connected to the connection point between the series arm resonators S4 and S5, and the other end is connected to the ground potential.

[0040] (Structure of elastic wave device)

[0041] Next, use Figure 2 and Figure 3 The basic structure of the elastic wave device 100 of this embodiment 1 will be described. Figure 2 This is a top view of the portion of the elastic wave device 100 where a common reflector is formed between adjacent resonators. Additionally, Figure 3 It is a cross-sectional view of the section between adjacent resonators.

[0042] Reference Figure 2 and Figure 3 The elastic wave device 100 includes two adjacent elastic wave resonators 101 and 102 and a common reflector REF12. The elastic wave resonators 101 and 102 included in the elastic wave device 100 correspond to... Figure 1 The resonator included in any one of the series arm resonant sections S1 to S5 and the parallel arm resonant sections P1 to P4 in the filter device 10 described herein.

[0043] Elastic wave resonators 101 and 102 are SAW resonators configured to include IDT electrodes. Specifically, elastic wave resonator 101 includes an IDT electrode IDT1 and reflectors REF1-1 and REF1-2 disposed on both sides of the IDT electrode IDT1. Elastic wave resonator 102 includes an IDT electrode IDT2 and reflectors REF2-1 and REF2-2 disposed on both sides of the IDT electrode IDT2.

[0044] In the IDT electrode, the surface acoustic wave propagates in a direction orthogonal to the extension direction of the opposing electrode finger. A reflector is used to reflect and confine the surface acoustic wave leaking from the end of the IDT electrode within the electrode. This improves the Q value of the elastic wave resonator.

[0045] like Figure 3 As shown, the IDT electrodes and reflectors constituting each elastic wave resonator are formed on a substrate 105 having a piezoelectric layer 110. In addition to the piezoelectric layer 110, the substrate 105 also includes a low-velocity layer 121, a high-velocity layer 122, and a support layer 130.

[0046] The support layer 130 is, for example, a semiconductor substrate formed of silicon (Si). On the support layer 130, facing... Figure 3 The positive direction of the Z-axis is composed of a high-velocity layer 122, a low-velocity layer 121, and a piezoelectric layer 110 stacked sequentially.

[0047] The piezoelectric layer 110 is formed, for example, of a piezoelectric single-crystal material such as lithium tantalate (LiTaO3) or lithium niobate (LiNbO3), or a piezoelectric laminate material including aluminum nitride (AlN), LiTaO3, or LiNbO3. An IDT electrode and a reflector, serving as functional elements, are formed on the upper surface (the plane in the positive Z-axis direction) of the piezoelectric layer 110. It should be noted that... Figure 3 In the example, lithium tantalate (LT) is used as the piezoelectric layer 110.

[0048] IDT electrodes and reflectors are formed, for example, of a single metal including at least one of aluminum, copper, silver, gold, titanium, tungsten, platinum, chromium, nickel, and molybdenum, or an alloy of these as the main components.

[0049] The low-velocity layer 121 is formed of a material whose volume wave velocity propagating in this low-velocity layer 121 is lower than that propagating in the piezoelectric layer 110. Figure 3 In the example, the low-velocity layer 121 is formed of silicon dioxide (SiO2). However, the low-velocity layer 121 is not limited to silicon dioxide; for example, it can also be formed of other dielectrics such as glass, silicon oxynitride, tantalum oxide, or compounds obtained by adding fluorine, carbon, boron, etc. to silicon dioxide.

[0050] Furthermore, the hypersonic layer 122 is formed of a material whose volume wave velocity propagating in the hypersonic layer 122 is higher than that of the elastic wave velocity propagating in the piezoelectric layer 110. Figure 3 In the example, the hypersonic layer 122 is formed of silicon nitride (SiN). However, the hypersonic layer 122 is not limited to silicon nitride, and can also be formed of materials such as aluminum nitride, alumina (bauxite), silicon oxynitride, silicon carbide, diamond-like carbon (DLC), and diamond.

[0051] By employing a structure in which a low-velocity layer 121 and a high-velocity layer 122 are stacked below the piezoelectric layer 110, the low-velocity layer 121 and the high-velocity layer 122 function as a reflective layer (mirror layer) 120. That is, surface acoustic waves leaking from the piezoelectric layer 110 towards the support layer 130 are reflected by the high-velocity layer 122 and confined within the low-velocity layer 121 due to the difference in propagation speeds. In this way, the acoustic energy loss of surface acoustic waves propagating through the reflective layer 120 is suppressed, thus enabling efficient propagation of surface acoustic waves. It should be noted that in... Figure 3In the example described, a low-speed sound layer 121 and a high-speed sound layer 122 are formed as a reflective layer 120, but the reflective layer 120 can also be a structure in which multiple low-speed sound layers 121 and high-speed sound layers 122 are arranged alternately.

[0052] Refer again Figure 2 The reflector REF1-1 of the elastic wave resonator 101 is disposed on the elastic wave resonator 102 side of the IDT electrode IDT1. The reflector REF1-2 is disposed on the opposite side of the reflector REF1-1 relative to the IDT electrode IDT1. The electrode fingers of the reflectors REF1-1 and REF1-2 are formed with the same spacing as the electrode fingers of the IDT electrode IDT1.

[0053] Furthermore, the reflector REF2-1 of the elastic wave resonator 102 is disposed on the elastic wave resonator 101 side of the IDT electrode IDT2. The reflector REF2-2 is disposed on the opposite side of the reflector REF2-1 relative to the IDT electrode IDT2. The electrode fingers of the reflectors REF2-1 and REF2-2 are formed with the same spacing as the electrode fingers of the IDT electrode IDT2.

[0054] A common reflector REF12 is disposed between reflector REF1-1 of elastic wave resonator 101 and reflector REF2-1 of elastic wave resonator 102. The sum of the number of electrode fingers of reflector REF1-1 and the number of electrode fingers of common reflector REF12 is set to be the same as the number of electrode fingers of reflector REF1-2. Similarly, the sum of the number of electrode fingers of reflector REF2-1 and the number of electrode fingers of common reflector REF12 is set to be the same as the number of electrode fingers of reflector REF2-2. The length of the electrode fingers of common reflector REF12 is the length above the cross width of the electrode fingers in the IDT electrodes included in elastic wave resonators 101 and 102.

[0055] The frequency characteristics of the shared reflector REF12 are intermediate between those of the elastic wave resonator 101 and the elastic wave resonator 102. By adopting such a structure, the shared reflector REF12 functions as a reflector for both the elastic wave resonator 101 and the elastic wave resonator 102.

[0056] In embodiment 1, an intermediate frequency characteristic is achieved by forming at least a portion of the electrode fingers of the common reflector REF12 with the spacing between the IDT electrode IDT1 in the elastic wave resonator 101 and the electrode fingers of reflectors REF1-1 and REF1-2 (first spacing: PT1) and the spacing between the IDT electrode IDT2 in the elastic wave resonator 102 and the electrode fingers of reflectors REF2-1 and REF2-2 (second spacing: PT2). Here, the spacing between the electrode fingers is the center-to-center distance between adjacent electrode fingers.

[0057] It should be noted that frequency characteristics can be measured by making contact with the probes connected to the network analyzer while minimizing the wiring that connects to each resonator and reflector.

[0058] It should be noted that in the shared reflector REF12, the electrode fingers can be formed with an intermediate spacing, or the spacing can be gradually changed from the elastic wave resonator 101 toward the elastic wave resonator 102. Alternatively, the spacing can be changed in stages from the elastic wave resonator 101 toward the elastic wave resonator 102.

[0059] The reflectors REF1-1 in elastic wave resonator 101 and REF2-1 in elastic wave resonator 102 are not necessarily required. Alternatively, a structure can be formed where only a shared reflector REF12 is configured between the IDT electrode IDT1 of elastic wave resonator 101 and the IDT electrode IDT2 of elastic wave resonator 102. In this case, it is preferable that the number of electrode fingers of the shared reflector REF12 is the same as the number of electrode fingers of reflectors REF1-2 and REF2-2.

[0060] Figure 4 This is a top view of adjacent resonators in the comparative example elastic wave device 100#. Elastic wave device 100# includes two adjacent elastic wave resonators 101# and 102#. In elastic wave device 100#, reflectors (REF1-2, REF2-2) of the same shape are arranged on both sides of the IDT electrode of each elastic wave resonator. That is, in each elastic wave resonator, the number of electrode fingers of the reflectors arranged on both sides is the same. Therefore, for example, if the number of electrode fingers of each reflector REF1-2, REF2-2 is 20, the total number of electrode fingers of the reflector arranged between the two IDT electrodes becomes 40.

[0061] On the other hand, in the elastic wave device 100 of Embodiment 1, for example, when the number of electrode fingers of each reflector REF1-1 and REF2-1 is set to 8, and the number of electrode fingers of the common reflector REF12 is set to 12, the total number of electrode fingers of reflector REF1-1 and common reflector REF12, and the total number of electrode fingers of reflector REF2-1 and common reflector REF12, are each 20, which is the same number as the number of electrode fingers of reflectors REF1-2 and REF2-2. However, the total number of electrode fingers of the reflectors disposed between the two IDT electrodes is reduced to 28. Therefore, the decrease in reflectivity can be suppressed by maintaining the number of electrode fingers that function as reflectors for each elastic wave resonator, and the interval between the two IDT electrodes can be narrowed. As a result, compared with the elastic wave device 100# of the comparative example, the elastic wave device 100 can be miniaturized.

[0062] Figure 5 This is a top view of the filter device of the elastic wave device in the comparative example and embodiment 1. Figure 5 (a) shows the structure of the elastic wave device including the comparative example. Figure 5 (b) shows the structure of the elastic wave device including Embodiment 1. Figure 5 In (a) and (b), the configuration of the external terminals (TX, ANT, GND), each resonator (S1-S5, P1-P4), and the wiring section 15 connecting these resonators is shown. The portion between the series arm resonator S2 (elastic wave resonators S21, S22) and the parallel arm resonator P1 (…) Figure 5 (b) region RG1) and the portion between the series arm resonator S4 (elastic wave resonators S41, S42) and the parallel arm resonator P4 ( Figure 5 The region RG2 of (b) applies the structure of this embodiment 1.

[0063] like Figure 5 As shown in (a), the width W1 of the filter device 10# is limited by the length of the adjacent portions of the elastic wave resonator. Therefore, as Figure 5 In the filter device 10 of (b), the elastic wave resonators are arranged adjacent to each other in the regions RG1 and RG2 using a common reflector. As a result, the width W2 of the filter device 10 can be narrowed (W2 < W1) compared to the case of the comparative example.

[0064] Figure 6 and Figure 7 These are for explanation Figure 5 A diagram showing the detailed structure of regions RG1 and RG2 in (b). Figure 6 and Figure 7In both cases, the structure becomes a shared reflector between a parallel arm resonator comprising one elastic wave resonator and a series arm resonator comprising two elastic wave resonators.

[0065] Reference Figure 6 The elastic wave resonator S21 is configured to include an IDT electrode IDT_S21 and reflectors REF_S21-1 and REF_S21-2, and the elastic wave resonator S22 is configured to include an IDT electrode IDT_S22 and reflectors REF_S22-1 and REF_S22-2. Furthermore, the elastic wave resonator constituting the parallel arm resonator P1 is configured to include an IDT electrode IDT_P1 and reflectors REF_P1-1 and REF_P1-2. Moreover, in these three elastic wave resonators, the common reflector REF_A is configured to be opposite to reflectors REF_S21-1, REF_S22-1, and REF_P1-1.

[0066] Reflectors REF_S21-1 and REF_S22-1 are arranged adjacent to each other on the first end side of the common reflector REF_A, and reflector REF_P1-1 is arranged on the second end side of the common reflector REF_A. The length of the electrode fingers of the common reflector REF_A is set to be longer than the length of the electrode fingers of reflector REF_P1-1, and longer than the sum of the lengths of the electrode fingers of reflector REF_S21-1 and reflector REF_S22-1.

[0067] By adopting such a structure, compared to configuring the reflectors separately for each elastic wave resonator, the length from the ends of reflectors REF_S21-2 and REF_S22-2 to the end of reflector REF_P1-2 can be shortened.

[0068] Reference Figure 7 The elastic wave resonator S41 is configured to include an IDT electrode IDT_S41 and reflectors REF_S41-1 and REF_S41-2, and the elastic wave resonator S42 is configured to include an IDT electrode IDT_S42 and reflectors REF_S42-1 and REF_S42-2. Furthermore, the elastic wave resonator constituting the parallel arm resonator P4 is configured to include an IDT electrode IDT_P4 and reflectors REF_P4-1 and REF_P4-2. Moreover, in these three elastic wave resonators, the common reflector REF_B is configured to be opposite to reflectors REF_S41-1, REF_S42-1, and REF_P4-1.

[0069] Reflectors REF_S41-1 and REF_S42-1 are arranged adjacent to each other on the first end side of the common reflector REF_B, and reflector REF_P4-1 is arranged on the second end side of the common reflector REF_B. The length of the electrode fingers of the common reflector REF_B is set to be longer than the length of the electrode fingers of reflector REF_P4-1, and longer than the sum of the lengths of the electrode fingers of reflector REF_S41-1 and reflector REF_S42-1.

[0070] By adopting such a structure, the length from the ends of reflectors REF_S41-2 and REF_S42-2 to the end of reflector REF_P4-2 can be shortened compared to the case where reflectors are configured separately for each elastic wave resonator.

[0071] Next, use Figure 8 and Figure 9 The reflection characteristics are explained when a shared reflector is used in adjacent elastic wave resonators. Figure 8 and Figure 9 In figures (a) and (b), the upper layer shows the frequency characteristics of the reflector's reflection coefficient, and the lower layer shows the frequency characteristics of the resonator's impedance. Figure 8 and Figure 9 In the diagram, solid lines LN10 and LN20 show series arm resonators, while dashed lines LN11 and LN21 show parallel arm resonators.

[0072] Reference Figure 8 ,exist Figure 1 In the trapezoidal filter shown, the resonant frequency of the series arm resonator is typically designed to be approximately the same as the anti-resonant frequency of the parallel arm resonator. That is, in the reflector of the series arm resonator, the stopband with a reflection coefficient close to 1 is between frequencies f2 and f4 (region AR10). On the other hand, in the reflector of the parallel arm resonator, the stopband with a reflection coefficient close to 1 is between frequencies f1 and f3 (region AR11).

[0073] Therefore, when a reflector shares a series arm resonator and a parallel arm resonator, and the spacing of the reflector's electrode fingers is set to the same as the spacing of the IDT electrodes of either resonator, while reflectivity can be ensured for the frequency range of f2–f3 (region AR15), the reflectivity may decrease significantly for the frequency range of f1–f2 or f3–f4. In this region of decreased reflectivity, surface acoustic waves from one resonator are not reflected and leak to the other, potentially leading to deterioration of the filter characteristics.

[0074] On the other hand, when at least a portion of the electrode finger spacing of the common reflector is set to the midpoint of the electrode finger spacing of the two resonators, as in Embodiment 1 of this application, the reflection coefficient of the common reflector becomes, for example, Figure 9 Like the single-dot dashed line LN12 in the image. Thus, as... Figure 9 As shown in (a), the stopband of the series arm resonator is extended to the frequency range of f2–f31 (region AR16). Similarly, as Figure 9 As shown in (b), the stopband of the parallel arm resonator is extended to the frequency range of f11 to f3 (region AR17). That is, the lower limit frequency of the stopband of the common reflector is between the lower limit frequency of the stopband of the first resonator and the lower limit frequency of the stopband of the second resonator, and the upper limit frequency of the stopband of the common reflector is between the upper limit frequency of the stopband of the first resonator and the upper limit frequency of the stopband of the second resonator. Therefore, compared with the case where the electrode finger spacing of the common reflector is uniformly equal to the electrode finger spacing of either resonator, the blocking range in the filter device can be expanded, resulting in the suppression of filter characteristic degradation.

[0075] It should be noted that in Embodiment 1, "stopband" refers to the frequency range with a reflection coefficient higher than 70% of the peak value of the reflection coefficient. In Embodiment 1, the lower limit frequency of the stopband corresponds to the resonant frequency of each resonator. Furthermore, the upper limit frequency of the stopband corresponds to the frequency at which stopband ripple begins to appear in the impedance characteristics of each resonator. Figure 8 The frequencies of regions RG10 and RG11 in the middle.

[0076] In each resonator, the intensity of the excited surface acoustic wave is maximized in the central region of the IDT electrodes, and monotonically decreases with increasing distance from the central region in the regions of the reflectors at both ends. Therefore, in the shared reflector, the greater the distance from the IDT electrodes, the smaller the effect of the decrease in reflectivity, even if the electrode finger spacing differs from that of the IDT electrodes. Thus, by setting the electrode finger spacing in the shared reflector to gradually or stepwise change from the electrode finger spacing of one resonator to that of the other, it is possible to ensure... Figure 9 The reflectivity between frequencies f1 to f11 and between frequencies f31 to f4 can further reduce the impact of reflectivity decrease.

[0077] It should be noted that, in cases such as Figure 9 When a shared reflector is used to make the series arm resonators and parallel arm resonators adjacent, the high-frequency and low-frequency ranges of the stopband become significantly narrower. Therefore, in trapezoidal filters, in order to maintain the steepness of the attenuation characteristics at the end of the overall passband, it is preferable not to use a shared reflector for the resonators forming the attenuation poles on the highest and lowest frequency sides.

[0078] Typically, in a trapezoidal filter, the attenuation electrode on the high-frequency side is formed by a series arm resonator, and the attenuation electrode on the low-frequency side is formed by a parallel arm resonator. Therefore, in a series arm resonator section that includes multiple series arm resonators, it is preferable to include a series arm resonator (third resonator) whose electrode finger spacing is set to be narrower than that of a series arm resonator (first resonator) using a common reflector.

[0079] Furthermore, in the parallel arm resonator section that includes multiple parallel arm resonators, it is preferable to include a parallel arm resonator (fourth resonator) in which the electrode finger spacing is set to be wider than that of the parallel arm resonator (second resonator) using a common reflector.

[0080] As described above, a common reflector is configured between two adjacent elastic wave resonators (first resonator and second resonator), and at least a portion of the electrode finger spacing of the common reflector is set to the distance between the electrode finger spacing of the IDT electrodes of the first resonator and the electrode finger spacing of the IDT electrodes of the second resonator to form an intermediate frequency characteristic. In this way, the decrease in the frequency characteristic of the elastic wave device can be suppressed, and the miniaturization of the elastic wave device can be achieved.

[0081] Figure 10 This diagram illustrates an example of the specifications of the elastic wave device 100 according to Embodiment 1. In this embodiment, resonator 1 has 130 pairs of IDT electrodes and 261 electrode fingers. The wavelength (=electrode finger spacing × 2) is 1.5495 μm, and the resonant frequency is 2453.39 MHz. On the other hand, resonator 2 has 90 pairs of IDT electrodes and 181 electrode fingers. The wavelength is 1.60700 μm, and the resonant frequency is 2358.11 MHz. The common reflector has 8 IDT fingers, and the reflectors disposed between the common reflector and each IDT electrode have 10 IDT fingers. It should be noted that the duty cycle in each resonator is 0.5. Furthermore, the electrode finger film thickness is the same for both resonator 1 and resonator 2.

[0082] In this embodiment, the wavelength of the common reflector gradually increases from 1.5495 μm to 1.90700 μm from resonator 1 towards resonator 2. Thus, by setting the wavelength (electrode finger spacing) of the common reflector to the midpoint between the wavelengths (electrode finger spacing) of the two resonators, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the miniaturization of the elastic wave device can be achieved. It should be noted that the electrode finger film thickness and duty cycle of resonators 1 and 2 are the same; therefore, the frequency of resonator 2, with its larger electrode finger spacing, is lower than the frequency of resonator 1.

[0083] (Variation Example 1)

[0084] exist Figure 2 In the elastic wave device 100 of Embodiment 1 shown, the following structure is described: two adjacent elastic wave resonators are configured such that the centers of the propagation directions of the surface acoustic waves are aligned, that is, aligned with the center of the cross width of the IDT electrodes and the direction orthogonal to the electrode fingers. However, the centers of the propagation directions of the surface acoustic waves may be different in the two elastic wave resonators.

[0085] Figure 11 This is a top view of the elastic wave device 100A of Modified Example 1. The elastic wave device 100A includes a device having... Figure 2 Elastic wave resonators 101A and 102A have the same structure, and a common reflector REF12A is disposed between elastic wave resonators 101A and 102A. Elastic wave resonator 101A includes IDT electrode IDT1A and reflectors REF1A-1 and REF1A-2. Elastic wave resonator 102A includes IDT electrode IDT2A and reflectors REF2A-1 and REF2A-2.

[0086] In the elastic wave device 100A, the propagation directions of the surface acoustic waves in the two elastic wave resonators 101A and 102A are staggered and do not overlap. Specifically, the virtual line CL1, which passes through the center of the cross width of the electrode fingers of the elastic wave resonator 101A and is orthogonal to the electrode fingers, and the virtual line CL2, which passes through the center of the cross width of the electrode fingers of the elastic wave resonator 102A and is orthogonal to the electrode fingers, are staggered in the extension direction of the electrode fingers.

[0087] The electrode finger of the common reflector REF12A has a length that is opposite to the electrode finger of reflector REF1A-1 in elastic wave resonator 101A and the electrode finger of reflector REF2A-1 in elastic wave resonator 102A.

[0088] It should be noted that this structure is also applied in Figure 6 and Figure 7 Regions RG1 and RG2 of the aforementioned filter device 10.

[0089] Thus, even when the propagation directions of surface acoustic waves in adjacent elastic wave resonators do not overlap, miniaturization of the elastic wave device can be achieved by using a common reflector with electrode fingers of the same length as the electrode fingers of each resonator, and the freedom of arrangement of functional elements on the substrate can be increased. Furthermore, assuming that even if surface acoustic waves leak from the common reflector, the leaked surface acoustic waves will enter the region of the other elastic wave resonator that is off-center from the cross-width of the IDT electrodes, the impact on the other elastic wave resonator can be reduced compared to the case where the propagation directions of the surface acoustic waves do not overlap.

[0090] (Variation Example 2)

[0091] In the elastic wave apparatus of Embodiment 1 and Modification 1, a structure was described in which the electrode fingers in the IDT electrode and reflector extend in a direction orthogonal to the busbar connected to the electrode fingers. In the elastic wave apparatus of Modification 2, a structure in which the electrode fingers of the IDT electrode and reflector are arranged at an angle relative to the busbar was described.

[0092] Figure 12 This is a top view of the elastic wave device 100B in Modification 2. The elastic wave device 100B includes elastic wave resonators 101B and 102B, and a common reflector REF12B disposed between the elastic wave resonators 101B and 102B. Similar to Modification 1, the elastic wave resonators 101B and 102B are disposed in offset positions.

[0093] The elastic wave resonator 101B includes an IDT electrode IDT1B and reflectors REF1B-1 and REF1B-2 disposed on both sides of the IDT electrode IDT1B. The elastic wave resonator 102B includes an IDT electrode IDT2B and reflectors REF2B-1 and REF2B-2 disposed on both sides of the IDT electrode IDT2B.

[0094] A common reflector REF12B is positioned between reflectors REF1B-1 and REF2B-1. The sum of the number of electrode fingers on reflector REF1B-1 and the number of electrode fingers on the common reflector REF12B is the same as the number of electrode fingers on reflector REF1B-2. Similarly, the sum of the number of electrode fingers on reflector REF2B-1 and the number of electrode fingers on the common reflector REF12B is the same as the number of electrode fingers on reflector REF2B-2. In the elastic wave device 100B, the electrode fingers of the elastic wave resonators 101B and 102B and the common reflector REF12B are connected at an angle relative to the busbar. The angle between the electrode fingers and the busbar is greater than 0° and less than 90°.

[0095] In an elastic wave resonator, the surface acoustic wave typically propagates in a direction orthogonal to the electrodes. That is, as... Figure 12 As shown, in elastic wave resonator 101B, the surface acoustic wave propagates in the direction of arrow RA1, and in elastic wave resonator 102B, the surface acoustic wave propagates in the direction of arrow RA2. Thus, by staggering adjacent elastic wave resonators and tilting the electrode fingers relative to the busbar, the propagation direction of the surface acoustic wave in one elastic wave resonator can be made outside the intersection width region of the electrode fingers in the IDT electrodes of the other elastic wave resonator. Therefore, the impact of surface acoustic wave leakage from the shared reflector on the other elastic wave resonator can be further reduced.

[0096] [Implementation Method 2]

[0097] In Embodiment 1, the following structure is described: In the case where the electrode finger spacing of adjacent elastic wave resonators is different, the electrode finger spacing of the common reflector is set to the middle spacing, thereby adjusting the frequency characteristics of the common reflector.

[0098] In Embodiment 2, the following structure is described: In the case where the duty cycles of the electrode fingers of adjacent elastic wave resonators are different, the duty cycle of the electrode fingers of the common reflector is set to the intermediate duty cycle, thereby adjusting the frequency characteristics of the common reflector. It should be noted that the duty cycle of the electrode fingers refers to the proportion of the electrode fingers relative to the distance between the electrode fingers (the width of the electrode fingers).

[0099] Figure 13 This is a cross-sectional view of the elastic wave device 100C according to Embodiment 2. The elastic wave device 100C includes elastic wave resonators 101C and 102C, and a common reflector REF12C disposed between the elastic wave resonators 101C and 102C.

[0100] A common reflector REF12C is disposed between reflector REF1C-1 disposed on one side of the IDT electrode IDT1C of elastic wave resonator 101C and reflector REF2C-1 disposed on one side of the IDT electrode IDT2C of elastic wave resonator 102C. It should be noted that in elastic wave device 100C, the electrode finger spacing of elastic wave resonator 101C and elastic wave resonator 102C are the same.

[0101] The duty cycle (first duty cycle) of the IDT electrode and the electrode fingers of the reflector in the elastic wave resonator 101C is set to DT1, and the duty cycle (second duty cycle) of the IDT electrode and the electrode fingers of the reflector in the elastic wave resonator 102C is set to DT2 (DT2 > DT1). Furthermore, at least a portion of the electrode fingers in the common reflector REF12C are formed with a duty cycle intermediate between the first duty cycle DT1 and the second duty cycle DT2. Preferably, the duty cycle of the electrode fingers of the common reflector REF12C is set to gradually or progressively increase from the elastic wave resonator 101C toward the elastic wave resonator 102C.

[0102] In this way, when the duty cycles of the electrode fingers in adjacent elastic wave resonators are different, the duty cycle is set to the middle value for at least a portion of the electrode fingers of the common reflector. This allows the frequency characteristics of the common reflector to be set to a value between the frequency characteristics of the two elastic wave resonators. Therefore, similar to Embodiment 1, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the elastic wave device can be miniaturized.

[0103] It should be noted that when the spacing and duty cycle of the electrode fingers in the two elastic wave resonators are different, the spacing and duty cycle of the electrode fingers in the shared reflector can also be set to an intermediate value.

[0104] Figure 14 This diagram illustrates an example of the specifications of the elastic wave device 100C according to Embodiment 2. In this embodiment, the number of IDT electrode pairs for each of resonator 1 and resonator 2 is 130, and the number of electrode fingers is 261. Furthermore, the wavelength (= spacing × 2) of each of resonator 1 and resonator 2 is 1.5495 μm. The number of IDT fingers in the common reflector is 8, and the number of IDT fingers in the reflectors disposed between the common reflector and each IDT electrode is 10. The resonant frequency of resonator 1 is 2453.39 MHz, and the resonant frequency of resonator 2 is 2446.86 MHz. It should be noted that resonator 1 and resonator 2 are identical.

[0105] In this embodiment, the duty cycle of resonator 1 is set to 0.5, and the duty cycle of resonator 2 is set to 0.55. The duty cycle in the common reflector gradually changes from 0.5 to 0.55 from resonator 1 towards resonator 2. Thus, by setting the duty cycle of the common reflector to the middle of the duty cycles of the two resonators, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the miniaturization of the elastic wave device can be achieved. It should be noted that the electrode finger spacing and electrode finger film thickness are the same for resonators 1 and 2; therefore, the frequency of resonator 2, with its larger duty cycle, is lower than the frequency of resonator 1.

[0106] [Implementation Method 3]

[0107] In Embodiment 3, the following structure is described: In the case where the electrode fingers of adjacent elastic wave resonators have different film thicknesses, the film thickness of the electrode fingers of the common reflector is set to the middle film thickness, thereby adjusting the frequency characteristics of the common reflector.

[0108] Figure 15 This is a cross-sectional view of the elastic wave device 100D according to Embodiment 3. The elastic wave device 100D includes elastic wave resonators 101D and 102D, and a common reflector REF12D disposed between the elastic wave resonators 101D and 102D.

[0109] The common reflector REF12D is disposed between reflector REF1D-1 disposed on one side of IDT electrode IDT1D of elastic wave resonator 101D and reflector REF2D-1 disposed on one side of IDT electrode IDT2D of elastic wave resonator 102D.

[0110] In the elastic wave device 100D, the spacing and duty cycle of the electrode fingers of the elastic wave resonator 101D are the same as those of the electrode fingers of the elastic wave resonator 102D, but the film thicknesses of the electrode fingers of the two elastic wave resonators 101D and 102D are different. Specifically, the film thickness of the electrode fingers of the elastic wave resonator 101D (the first electrode finger film thickness) is set to ET1, and the film thickness of the electrode fingers of the elastic wave resonator 102D (the second electrode finger film thickness) is set to ET2 (ET2 > ET1).

[0111] Furthermore, at least a portion of the film thickness of the electrode fingers in the shared reflector REF12D is formed at an intermediate thickness between the aforementioned first electrode finger film thickness ET1 and second electrode finger film thickness ET2. In other words, at least a portion of the film thickness of the electrode fingers in the shared reflector REF12D is thicker than the first electrode finger film thickness ET1 and thinner than the second electrode finger film thickness ET2. Preferably, the film thickness of the electrode fingers of the shared reflector REF12D is set to gradually or progressively increase in thickness from the elastic wave resonator 101D toward the elastic wave resonator 102D.

[0112] In this way, when the film thickness of the electrode fingers in adjacent elastic wave resonators is different, the film thickness is set to an intermediate value for at least a portion of the electrode fingers of the common reflector. This allows the frequency characteristics of the common reflector to be set to a value between the frequency characteristics of the two elastic wave resonators. Therefore, similar to Embodiment 1, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the elastic wave device can be miniaturized.

[0113] It should be noted that in two elastic wave resonators, where the spacing and / or duty cycle of the electrode fingers differ in addition to the film thickness of the electrode fingers, the spacing and / or duty cycle of the electrode fingers for the common reflector can also be set to an intermediate value.

[0114] Figure 16 This diagram illustrates an example of the specifications of the elastic wave device 100D according to Embodiment 3. In this embodiment, the resonator 1 has 130 pairs of IDT electrodes and 261 electrode fingers. On the other hand, the resonator 2 has 90 pairs of IDT electrodes and 181 electrode fingers. The wavelength (= spacing × 2) of both resonators 1 and 2 is 1.5495 μm. The common reflector has 8 IDT fingers, and the reflectors disposed between the common reflector and each IDT electrode have 10 IDT fingers. The resonant frequency of resonator 1 is 2453.39 MHz, and the resonant frequency of resonator 2 is 2442.24 MHz. It should be noted that the duty cycle of the IDT electrodes in both resonators 1 and 2 is 0.5.

[0115] In this embodiment, the film thickness of the electrode fingers in resonator 1 is set to 121 nm, and the film thickness of the electrode fingers in resonator 2 is set to 131 nm. The thickness gradually increases from 121 nm to 131 nm from resonator 1 towards resonator 2. Thus, by setting the film thickness of the electrode fingers in the shared reflector to the middle of the film thicknesses of the electrode fingers in the two resonators, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the miniaturization of the elastic wave device can be achieved. It should be noted that the electrode finger spacing and duty cycle of resonators 1 and 2 are the same; therefore, the frequency of resonator 2, which has a thicker electrode finger film, is lower than the frequency of resonator 1.

[0116] [Implementation Method 4]

[0117] In elastic wave devices, dielectric layers are sometimes disposed on the IDT electrodes and reflectors to protect the functional components on the substrate. The frequency characteristics of the elastic wave resonator also vary depending on the thickness of the protective dielectric layer.

[0118] In embodiment 4, the following structure is described: In the case where the thickness of the protective dielectric layer in adjacent elastic wave resonators is different, the thickness of the dielectric layer is set to the middle thickness, thereby adjusting the frequency characteristics of the shared reflector.

[0119] Figure 17 This is a cross-sectional view of the elastic wave device 100E according to Embodiment 4. The elastic wave device 100E includes elastic wave resonators 101E and 102E, a common reflector REF12E disposed between the elastic wave resonators 101E and 102E, and a dielectric layer 140 disposed on the elastic wave resonators 101E, 102E and the common reflector REF12E.

[0120] A common reflector REF12E is disposed between reflector REF1E-1 disposed on one side of the IDT electrode IDT1E of the elastic wave resonator 101E and reflector REF2E-1 disposed on one side of the IDT electrode IDT2E of the elastic wave resonator 102E. In the elastic wave device 100E, the spacing, duty cycle, and film thickness of the IDT electrodes and reflectors of the elastic wave resonators 101E and 102E, as well as the electrode fingers in the common reflector REF12E, are set to the same values.

[0121] The dielectric layer 140 may be made of materials such as silicon dioxide, glass, silicon oxynitride, tantalum oxide, silicon nitride, aluminum nitride, alumina (bauxite), silicon oxynitride, silicon carbide, diamond-like carbon (DLC), or diamond. It may also be formed from compounds obtained by adding fluorine, carbon, boron, etc., to silicon dioxide. The dielectric layer 140 is configured to cover functional elements (IDT electrodes, reflectors) disposed on the piezoelectric layer 110 of the substrate 105. The thickness of the dielectric layer 140 disposed in the region of the elastic wave resonator 101E (first dielectric thickness) is set to FT1, and the thickness of the dielectric layer 140 disposed in the region of the elastic wave resonator 102E (second dielectric thickness) is set to FT2 (FT1 < FT2). When the dielectric layer 140 is formed of a material (silicon dioxide, glass, tantalum oxide, niobium oxide, tellurium oxide, etc.) with a sound velocity slower than the resonant frequency of an elastic wave resonator, the thicker the dielectric layer disposed on the electrode fingers, the greater the mass of the electrode fingers during vibration, and therefore, the lower the resonant frequency of the resonator. Therefore, in Figure 17 In the structure, the resonant frequency of elastic wave resonator 102E is lower than that of elastic wave resonator 101E.

[0122] On the other hand, when the dielectric layer 140 is formed of a material (glass, silicon nitride, aluminum nitride, bauxite, silicon oxynitride, silicon carbide, DLC, diamond, etc.) with a sound velocity faster than that of a resonant resonator, the thicker the dielectric layer, the higher the resonant frequency of the resonator.

[0123] It should be noted that, in Embodiment 4, the film thicknesses FT1 and FT2 of the dielectric layer 140 are defined as the distances from the upper surface of the IDT electrode and the electrode fingers of the reflector to the surface of the dielectric layer 140. Additionally, as... Figure 18 As shown, the dielectric layer 140 may also be such that the position of the upper surface of the dielectric with electrode fingers is different from the position of the upper surface of the dielectric without electrode fingers.

[0124] Furthermore, at least a portion of the dielectric layer 140 disposed in the region of the common reflector REF12E has a film thickness intermediate between the first dielectric film thickness FT1 and the second dielectric film thickness FT2. In other words, at least a portion of the dielectric layer 140 disposed in the region of the common reflector REF12E has a film thickness thinner than the first dielectric film thickness FT1 and thicker than the second dielectric film thickness FT2. Preferably, the film thickness of the dielectric layer 140 disposed in the region of the common reflector REF12E is set to gradually or progressively thin from the elastic wave resonator 101E toward the elastic wave resonator 102E.

[0125] In this way, when the thickness of the protective dielectric layer in the regions of adjacent elastic wave resonators is different, by setting at least a portion of the dielectric layer in the region of the common reflector to an intermediate thickness, the frequency characteristics of the common reflector can be set to the frequency characteristics between the two elastic wave resonators. Therefore, similar to Embodiment 1, the decrease in the frequency characteristics of the elastic wave device can be suppressed, and the elastic wave device can be miniaturized.

[0126] It should be noted that in two elastic wave resonators, where the electrode finger spacing, duty cycle, and / or film thickness differ in addition to the dielectric layer thickness, the electrode finger spacing, duty cycle, and / or film thickness for the common reflector can also be set to intermediate values.

[0127] Furthermore, the resonant frequency, stopband frequency (upper and lower limits), and reflector frequency (upper and lower limits) of a resonator typically exhibit the same dependence on parameters such as the finger spacing, finger duty cycle, finger thickness, piezoelectric layer thickness, and dielectric layer thickness. As mentioned above, the larger the parameters of finger spacing, finger duty cycle, and finger thickness, the lower the resonant frequency tends to be for each resonator. Therefore, regarding the common reflector REF12 (REF12C, REF12D, REF12E) and elastic wave resonators 101 (101C, 101D, 101E) and 102 (102C, 102D, 102E), when the value obtained by multiplying the distance between the electrode fingers, the duty cycle of the electrode fingers, and the thickness of the electrode fingers (= electrode finger distance × electrode finger duty cycle × electrode finger thickness) is set as the first value, the second value, and the third value, respectively, the first value of the common reflector REF12 is set to be between the second value of the elastic wave resonator 101 and the third value of the elastic wave resonator 102.

[0128] Furthermore, when the common reflector REF12 covers the elastic wave resonator 101, elastic wave resonator 102, and the common reflector REF12, and is made of a dielectric layer composed of a material having a sound velocity of volume waves that is slower than the resonant frequency of the elastic wave resonator, the greater the thickness of the dielectric layer, the lower the resonant frequency of each resonator tends to be. Therefore, regarding the common reflector REF12 and the elastic wave resonators 101 and 102, when the value obtained by multiplying the distance between the electrode fingers, the duty cycle of the electrode fingers, the thickness of the electrode fingers, and the thickness of the dielectric layer (= electrode finger distance × electrode finger duty cycle × electrode finger thickness × dielectric layer thickness) is set as the fourth, fifth, and sixth values, respectively, the fourth value of the common reflector REF12 is set to be between the fifth value of the elastic wave resonator 101 and the sixth value of the elastic wave resonator 102.

[0129] Alternatively, when the elastic wave resonator 101, elastic wave resonator 102, and common reflector REF12 are covered by a dielectric layer made of a material with a sound velocity of volume waves that is faster than the resonant frequency of the elastic wave resonator, the greater the thickness of the dielectric layer, the higher the resonant frequency of each resonator tends to be. Therefore, regarding the common reflector REF12 and elastic wave resonators 101 and 102, when the value obtained by multiplying the distance between the electrode fingers, the duty cycle of the electrode fingers, the thickness of the electrode fingers, and the inverse of the thickness of the dielectric layer (= electrode finger distance × electrode finger duty cycle × electrode finger thickness / dielectric layer thickness) is set as the seventh, eighth, and ninth values ​​respectively, the seventh value of the common reflector REF12 is set to be between the eighth value of the elastic wave resonator 101 and the ninth value of the elastic wave resonator 102.

[0130] It should be noted that in order for the relationships between the first and third values, the fourth and sixth values, and the seventh and ninth values ​​to hold true, it is necessary to use regions where each parameter changes approximately linearly. Therefore, the duty cycle of each elastic wave resonator needs to be below 0.65.

[0131] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the invention is defined by the claims, rather than by the description of the embodiments above, and is intended to include all modifications within the same meaning and scope as the claims.

[0132] Explanation of reference numerals in the attached figures

[0133] 10, 10# Filter device; 15 Wiring section; 100, 100A~100E, 100# Elastic wave device; 101, 101A~101E, 101#, 102, 102A~102E, 102#, S21, S22, S31, S32, S41, S42 Elastic wave resonators; 105 Substrate; 110 Piezoelectric layer; 120 Reflective layer; 121 Low-velocity layer; 122 High-velocity layer; 130 Support layer; 140 Dielectric layer; ANT antenna terminal; IDT1, IDT1A~IDT1E, IDT2, IDT2A~IDT2E IDT electrodes; P1~P4 Parallel arm resonator, REF1, REF1A~REF1E, REF2, REF2A~REF2E, REF_P1, REF_P4, REF_S21, REF_S22, REF_S41, REF_S42 reflectors, REF12, REF12A~REF12E, REF_A, REF_B shared reflector, S1~S5 series arm resonator, TX transmitting terminal.

Claims

1. An elastic wave device, comprising: A substrate having a piezoelectric layer; A first resonator is disposed on the substrate; A second resonator, disposed adjacent to the first resonator on the substrate, has a different frequency response than the first resonator; and A shared reflector is disposed on the substrate between the first resonator and the second resonator, functioning as a reflector for both the first and second resonators. The first resonator includes a first IDT electrode in which electrode fingers are formed at a first pitch, wherein IDT stands for interdigital transducer. The second resonator includes a second IDT electrode with electrode fingers formed at a second spacing. The lower stopband frequency of the common reflector is the same as the lower stopband frequency of the first resonator and the lower stopband frequency of the second resonator, or it is between the lower stopband frequencies of the first resonator and the second resonator. The upper limit frequency of the stopband of the common reflector is the same as the upper limit frequency of the stopband of the first resonator and the upper limit frequency of the stopband of the second resonator, or it is between the upper limit frequency of the stopband of the first resonator and the upper limit frequency of the stopband of the second resonator. The elastic wave device further includes a dielectric layer disposed on the first resonator, the second resonator, and the common reflector. The dielectric layer disposed in the region of the first resonator is thicker than the dielectric layer disposed in the region of the second resonator. At least a portion of the dielectric layer disposed in the region of the common reflector is thinner than the dielectric layer disposed in the region of the first resonator and thicker than the dielectric layer disposed in the region of the second resonator.

2. The elastic wave device according to claim 1, wherein, The second spacing is narrower than the first spacing. The electrodes of the shared reflector are formed at least a portion of the distance between the first spacing and the second spacing.

3. The elastic wave device according to claim 2, wherein, The spacing between the electrode fingers of the shared reflector gradually narrows from the first resonator toward the second resonator.

4. The elastic wave device according to claim 2, wherein, The spacing between the electrode fingers of the shared reflector narrows in stages from the first resonator toward the second resonator.

5. The elastic wave device according to claim 1, wherein, The electrode fingers in the first resonator have a first duty cycle, and the electrode fingers in the second resonator have a second duty cycle, which is larger than the first duty cycle. The electrodes of the shared reflector are formed at least a portion of the duty cycle between the first duty cycle and the second duty cycle.

6. The elastic wave device according to claim 5, wherein, The duty cycle of the electrodes of the shared reflector gradually increases from the first resonator toward the second resonator.

7. The elastic wave device according to claim 5, wherein, The duty cycle of the electrodes of the shared reflector increases in stages from the first resonator toward the second resonator.

8. The elastic wave device according to claim 1, wherein, The electrode fingers of the first resonator are thinner than the electrode fingers of the second resonator. At least a portion of the electrode fingers of the common reflector are thicker than the electrode fingers of the first resonator and thinner than the electrode fingers of the second resonator.

9. The elastic wave device according to any one of claims 1 to 8, wherein, The first resonator and the second resonator each include: A first reflector, disposed between the IDT electrode included in the resonator and the common reflector; and The second reflector is positioned at the end opposite to the first reflector relative to the IDT electrode. The electrode fingers of the first reflector of the first resonator are formed with the first spacing. The electrode fingers of the first reflector of the second resonator are formed with the second spacing.

10. The elastic wave device according to claim 9, wherein, The sum of the number of electrode fingers of the first reflector and the common reflector is the same as the number of electrode fingers of the second reflector.

11. The elastic wave device according to any one of claims 1 to 8, wherein, The length of the electrode fingers of the common reflector is greater than or equal to the cross width of the electrode fingers in the IDT electrodes of each resonator.

12. The elastic wave device according to any one of claims 1 to 8, wherein, The first virtual line does not overlap with the second virtual line. The first virtual line passes through the center of the cross width of the first IDT electrode and is orthogonal to the electrode finger of the first IDT electrode. The second virtual line passes through the center of the cross width of the second IDT electrode and is orthogonal to the electrode finger of the second IDT electrode.

13. The elastic wave device according to any one of claims 1 to 8, wherein, Each IDT electrode and each reflector includes the busbar connected to the electrode fingers. In each IDT electrode and each reflector, the angle between the electrode finger and the bus bar is greater than 0° and less than 90°.

14. The elastic wave device according to any one of claims 1 to 8, wherein, The substrate further includes a reflective layer on which the piezoelectric layer is disposed.

15. An elastic wave device, comprising: A substrate having a piezoelectric layer; A first resonator is disposed on the substrate; A second resonator, disposed adjacent to the first resonator on the substrate, has a different frequency response than the first resonator; and A shared reflector is disposed on the substrate between the first resonator and the second resonator, functioning as a reflector for both the first and second resonators. The first resonator includes a first IDT electrode forming electrode fingers with a first spacing. The second resonator includes a second IDT electrode with electrode fingers formed at a second spacing. Regarding the shared reflector, the first resonator, and the second resonator, when the values ​​obtained by multiplying the spacing of the electrode fingers, the duty cycle of the electrode fingers, and the thickness of the electrode fingers are respectively set as the first value, the second value, and the third value, the first value is the same as the second value and the third value, or is between the second value and the third value. The elastic wave device further includes a dielectric layer configured to cover the first resonator, the second resonator, and the common reflector. The dielectric layer is formed of a material having a volume wave velocity that is slower than the resonant frequencies of the first and second resonators. Regarding the shared reflector, the first resonator, and the second resonator, when the value obtained by multiplying the spacing of the electrode fingers, the duty cycle of the electrode fingers, the thickness of the electrode fingers, and the thickness of the dielectric layer is set as the fourth value, the fifth value, and the sixth value, respectively, the fourth value is the same as the fifth value and the sixth value, or is between the fifth value and the sixth value.

16. An elastic wave device, comprising: A substrate having a piezoelectric layer; A first resonator is disposed on the substrate; A second resonator, disposed adjacent to the first resonator on the substrate, has a different frequency response than the first resonator; and A shared reflector is disposed on the substrate between the first resonator and the second resonator, functioning as a reflector for both the first and second resonators. The first resonator includes a first IDT electrode forming electrode fingers with a first spacing. The second resonator includes a second IDT electrode with electrode fingers formed at a second spacing. Regarding the shared reflector, the first resonator, and the second resonator, when the values ​​obtained by multiplying the spacing of the electrode fingers, the duty cycle of the electrode fingers, and the thickness of the electrode fingers are respectively set as the first value, the second value, and the third value, the first value is the same as the second value and the third value, or is between the second value and the third value. The elastic wave device further includes a dielectric layer configured to cover the first resonator, the second resonator, and the common reflector. The dielectric layer is formed of a material having a volume wave velocity that is faster than the resonant frequencies of the first and second resonators. Regarding the shared reflector, the first resonator, and the second resonator, when the value obtained by multiplying the distance between the electrode fingers, the duty cycle of the electrode fingers, the thickness of the electrode fingers, and the inverse of the thickness of the dielectric layer is set as the seventh value, the eighth value, and the ninth value, respectively, the seventh value is the same as the eighth value and the ninth value, or is between the eighth value and the ninth value.

17. A trapezoidal filter comprising the elastic wave device according to any one of claims 1 to 16, The trapezoidal filter has the following features: Multiple series-arm resonators, including the first resonator; and Multiple parallel arm resonators, including the second resonator, The plurality of series-arm resonators also includes a third resonator, the spacing of which is narrower than that of the first resonator.

18. A trapezoidal filter comprising the elastic wave device according to any one of claims 1 to 16, The trapezoidal filter has the following features: Multiple series-arm resonators, including the first resonator; and Multiple parallel arm resonators, including the second resonator, The plurality of parallel arm resonators also includes a fourth resonator, the spacing of which is wider than that of the second resonator.

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