Filter and communication device

Abstract

To improve the frequency characteristics of a filter configured using a resonator.SOLUTION: In a ladder-type filter including a plurality of parallel arm resonators KP and a plurality of series arm resonators, the parallel arm resonators KP have a first piezoelectric body portion 1, a first IDT electrode 2 located in a layer higher than the first piezoelectric body portion and including a first electrode finger 8 and a second electrode finger 9 adjacent to each other, and a first region 12, a second region 13, a third region 14, and a fourth region 15. The series arm resonators have a second piezoelectric body portion, a second IDT electrode located in a layer higher than the second piezoelectric body portion and including a third electrode finger and a fourth electrode finger adjacent to each other, and a fifth region, a sixth region, a seventh region, and an eighth region. When a difference between sound velocity in the third region and sound velocity in the fourth region is defined as a first sound velocity difference and a difference between sound velocity in the seventh region and sound velocity in the eighth region is defined as a second sound velocity difference, the first sound velocity difference is larger than the second sound velocity difference.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a filter and a communication device. [Background technology]

[0002] Patent Document 1 discloses an acoustic wave device in which first electrode fingers have widened portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 100949 Summary of the Invention [Problem to be solved by the invention]

[0004] In a filter configured using an acoustic wave device, it is expected that the disadvantages of the acoustic wave device can be reduced and the frequency characteristics of the filter can be improved. [Means for solving the problem]

[0005] A filter according to an embodiment of the present disclosure includes a parallel arm resonator and a series arm resonator. The parallel arm resonator has a first piezoelectric body portion and a first IDT electrode located in a layer higher than the first piezoelectric body portion and including first and second electrode fingers adjacent to each other. The series arm resonator has a second piezoelectric body portion and a second IDT electrode located in a layer higher than the second piezoelectric body portion and including third and fourth electrode fingers adjacent to each other. When an arrangement direction of the first electrode fingers and the second electrode fingers is defined as a first arrangement direction and an arrangement direction of the third electrode fingers and the fourth electrode fingers is defined as a second arrangement direction, the first electrode fingers have a first region facing tips of the second electrode fingers in the first arrangement direction and a second region facing the tips of the first electrode fingers from the first region. the parallel arm resonator includes a third region including the second region and extending in the first arrangement direction, and a fourth region including the first region and extending in the first arrangement direction, the third electrode finger includes a fifth region facing a tip of the fourth electrode finger in the second arrangement direction and a sixth region located closer to the tip of the third electrode finger than the fifth region, and the series arm resonator includes a seventh region including the sixth region and extending in the second arrangement direction, and an eighth region including the fifth region and extending in the second arrangement direction, wherein a first sound velocity difference is a difference between the sound velocity in the third region and the sound velocity in the fourth region, and a second sound velocity difference is a difference between the sound velocity in the seventh region and the sound velocity in the eighth region, the first sound velocity difference is greater than the second sound velocity difference. Effect of the Invention

[0006] According to one aspect of the present disclosure, it is possible to improve the frequency characteristics of a filter configured using a resonator. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a filter according to a first embodiment of the present disclosure. [Diagram 2] 2 is a plan view showing a schematic configuration example of a parallel arm resonator. FIG. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] 2 is a plan view showing a schematic configuration example of a series arm resonator; FIG. [Diagram 5] 5 is a cross-sectional view of FIG. 4 taken along line B-B. [Figure 6] 4 is a graph showing an example of the relationship between frequency and impedance in the parallel arm resonator shown in FIGS. 2 and 3. [Figure 7] 1 is a graph showing the relationship between frequency and transmission characteristics of an example and a comparative example. [Figure 8] 1 is a graph showing the relationship between frequency and transmission characteristics of an example and a comparative example. [Figure 9] 11 is a graph showing the relationship of impedance phase to frequency in an embodiment. [Figure 10] 13 is a graph showing the relationship of impedance phase with respect to frequency in a comparative example. [Figure 11] 10 is a cross-sectional view showing a schematic configuration of a resonator according to a second embodiment of the present disclosure. [Figure 12] FIG. 11 is a schematic diagram of a communication device according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0009] [Embodiment 1] FIG. 1 is a schematic diagram of a filter 101 according to a first embodiment of the present disclosure.

[0010] The filter 101 includes a parallel arm resonator KP and a series arm resonator KS. The filter 101 is a ladder-type filter including multiple parallel arm resonators KP and multiple series arm resonators KS. As an example, the filter 101 includes, in order from the input terminal IN side of the filter 101, a parallel arm resonator KP1, a parallel arm resonator KP2, and a parallel arm resonator KP3. As an example, the filter 101 includes, in order from the input terminal IN side of the filter 101, a series arm resonator KS1, a series arm resonator KS2, a series arm resonator KS3, and a series arm resonator KS4. In FIG. 1, the symbol OUT denotes the output terminal of the filter 101.

[0011] The multiple series arm resonators KS are connected in series with each other. The multiple parallel arm resonators KP are connected in parallel to a series circuit of the multiple series arm resonators KS. At least one parallel arm resonator KP is connected between every two adjacent series arm resonators KS. The parallel arm resonators KP may be grounded.

[0012] Fig. 2 is a plan view showing a schematic configuration example of a parallel arm resonator KP. Fig. 3 is a cross-sectional view taken along line AA in Fig. 2. All of the parallel arm resonators KP included in the filter 101 may have the configuration shown in Fig. 2 and Fig. 3, or at least one of them may have a configuration different from that shown in Fig. 2 and Fig. 3.

[0013] The parallel arm resonator KP has a first piezoelectric portion 1, a first IDT electrode 2, a first dielectric layer 3, a plurality of first multilayer reflective films 4, and a first support substrate 5. The first support substrate 5, the plurality of first multilayer reflective films 4, the first piezoelectric portion 1, the first IDT electrode 2, and the first dielectric layer 3 are laminated in this order. Each of the plurality of first multilayer reflective films 4 has, in order from the first piezoelectric portion 1 side, a first low acoustic impedance layer 6 and a first high acoustic impedance layer 7. As an example, the number of first multilayer reflective films 4 in the parallel arm resonator KP is four. IDT is an abbreviation for interdigital transducer.

[0014] The first piezoelectric part 1 may include at least one of LiTaO3 and LiNbO3. LiTaO3 may be called lithium tantalate and may be written as LT. LiNbO3 may be called lithium niobate and may be written as LN. The thickness of the first piezoelectric part 1 is T1.

[0015] The first IDT electrode 2 is located in a layer above the first piezoelectric portion 1. The first IDT electrode 2 includes a first electrode finger 8, a second electrode finger 9, a first bus bar 10, and a second bus bar 11. The first electrode finger 8 and the second electrode finger 9 are adjacent to each other. The first bus bar 10 is electrically connected to the first electrode finger 8. The second bus bar 11 is electrically connected to the second electrode finger 9.

[0016] The first dielectric layer 3 is located above the first IDT electrode 2. The first dielectric layer 3 may include at least one of a first high acoustic velocity dielectric material and Ta2O5. The first high acoustic velocity dielectric material may be defined as a material in which the acoustic velocity in the first high acoustic velocity dielectric material is higher than the acoustic velocity in the first piezoelectric portion 1. The first high acoustic velocity dielectric material may be any of SiO2, AlN, SiN, Al2O3, and TiO2. By using the first high acoustic velocity dielectric material, the amount of reduction in acoustic velocity caused by the first dielectric layer 3 relative to the thickness of the first dielectric layer 3 can be reduced.

[0017] The first multilayer reflective film 4, i.e., the first low acoustic impedance layer 6 and the first high acoustic impedance layer 7, are located below the first piezoelectric portion 1. The acoustic impedance of the first low acoustic impedance layer 6 is lower than the acoustic impedance of the first high acoustic impedance layer 7. The first low acoustic impedance layer 6 may contain SiO2. The first high acoustic impedance layer 7 may contain at least one of HfO2, Ta2O5, and ZrO2. The parallel arm resonator KP may be interpreted as a multilayer reflective film structure including the first multilayer reflective film 4.

[0018] The first supporting substrate 5 supports the first piezoelectric portion 1, the first IDT electrode 2, the first dielectric layer 3, and the plurality of first multilayer reflective films 4. The first supporting substrate 5 may be a Si substrate.

[0019] 2 and 3 show a first arrangement direction DL1, a first direction D1, and a second direction D2. The first arrangement direction DL1 can be defined as the arrangement direction of the first electrode fingers 8 and the second electrode fingers 9. The first direction D1 can be defined as the longitudinal direction of the first electrode fingers 8 and the longitudinal direction of the second electrode fingers 9. The second direction D2 can be defined as the thickness direction of the first piezoelectric portion 1. The first arrangement direction DL1, the first direction D1, and the second direction D2 may be perpendicular to each other.

[0020] The first electrode finger 8 includes a first region 12 and a second region 13. The parallel arm resonator KP includes a third region 14 and a fourth region 15. The first region 12 is a region facing the tip portion 16 of the second electrode finger 9 in the first arrangement direction DL1. The second region 13 is a region located closer to the tip portion 17 of the first electrode finger 8 than the first region 12. The third region 14 is a region including the second region 13 and extending in the first arrangement direction DL1. The fourth region 15 is a region including the first region 12 and extending in the first arrangement direction DL1.

[0021] In the description of the embodiments of the present disclosure, the term "edge" refers to a point at the edge of an object, and the term "end" refers to a region at the edge of an object. In other words, the term "edge" can be interpreted as a region that includes the "edge."

[0022] The difference between the sound speed in the third region 14 and the sound speed in the fourth region 15 is defined as a first sound speed difference.

[0023] When the speed of sound in third region 14 is not constant with respect to the position in third region 14, the speed of sound in third region 14 may be any of the average value, maximum value, minimum value, and other representative value of the multiple speeds of sound in third region 14. When the speed of sound in fourth region 15 is not constant with respect to the position in fourth region 15, the speed of sound in fourth region 15 may be any of the average value, maximum value, minimum value, and other representative value of the multiple speeds of sound in fourth region 15.

[0024] Fig. 4 is a plan view showing a schematic configuration example of a series arm resonator KS. Fig. 5 is a cross-sectional view taken along line BB of Fig. 4. All of the multiple series arm resonators KS included in the filter 101 may have the configuration shown in Fig. 4 and Fig. 5, or at least one of them may have a configuration different from that shown in Fig. 4 and Fig. 5.

[0025] The series arm resonator KS has a second piezoelectric portion 18, a second IDT electrode 19, a second dielectric layer 20, a plurality of second multilayer reflective films 21, and a second support substrate 22. The second support substrate 22, the plurality of second multilayer reflective films 21, the second piezoelectric portion 18, the second IDT electrode 19, and the second dielectric layer 20 are laminated in this order. Each of the plurality of second multilayer reflective films 21 has, in this order from the second piezoelectric portion 18 side, a second low acoustic impedance layer 23 and a second high acoustic impedance layer 24. As an example, the number of second multilayer reflective films 21 in the series arm resonator KS is four.

[0026] The second piezoelectric portion 18 may include at least one of LT and LN. The second piezoelectric portion 18 has a thickness T18.

[0027] The second IDT electrode 19 is located in a layer above the second piezoelectric portion 18. The second IDT electrode 19 includes a third electrode finger 25, a fourth electrode finger 26, a third bus bar 27, and a fourth bus bar 28. The third electrode finger 25 and the fourth electrode finger 26 are adjacent to each other. The third bus bar 27 is electrically connected to the third electrode finger 25. The fourth bus bar 28 is electrically connected to the fourth electrode finger 26.

[0028] The second dielectric layer 20 is located above the second IDT electrode 19. The second dielectric layer 20 may include at least one of a second high acoustic velocity dielectric material and Ta2O5. The second high acoustic velocity dielectric material may be defined as a material in which the acoustic velocity in the second high acoustic velocity dielectric material is higher than the acoustic velocity in the second piezoelectric portion 18. The second high acoustic velocity dielectric material may be any of SiO2, AlN, SiN, Al2O3, and TiO2. By using the second high acoustic velocity dielectric material, the amount of reduction in acoustic velocity caused by the second dielectric layer 20 relative to the thickness of the second dielectric layer 20 can be reduced.

[0029] The second multilayer reflective film 21, i.e., the second low acoustic impedance layer 23 and the second high acoustic impedance layer 24, are located below the second piezoelectric portion 18. The acoustic impedance of the second low acoustic impedance layer 23 is lower than the acoustic impedance of the second high acoustic impedance layer 24. The second low acoustic impedance layer 23 may contain SiO2. The second high acoustic impedance layer 24 may contain at least one of HfO2, Ta2O5, and ZrO2. The series arm resonator KS may be interpreted as a multilayer reflective film structure including the second multilayer reflective film 21.

[0030] The second support substrate 22 supports the second piezoelectric portion 18, the second IDT electrode 19, the second dielectric layer 20, and a plurality of second multilayer reflective films 21. The second support substrate 22 may be a Si substrate.

[0031] 4 and 5 show a second arrangement direction DL2, a third direction D3, and a fourth direction D4. The second arrangement direction DL2 can be defined as the arrangement direction of the third electrode fingers 25 and the fourth electrode fingers 26. The third direction D3 can be defined as the longitudinal direction of the third electrode fingers 25 and the longitudinal direction of the fourth electrode fingers 26. The fourth direction D4 can be defined as the thickness direction of the second piezoelectric portion 18. The second arrangement direction DL2, the third direction D3, and the fourth direction D4 may be perpendicular to each other.

[0032] The third electrode finger 25 includes a fifth region 29 and a sixth region 30. The series arm resonator KS includes a seventh region 31 and an eighth region 32. The fifth region 29 faces the tip 33 of the fourth electrode finger 26 in the second arrangement direction DL2. The sixth region 30 is located closer to the tip 34 of the third electrode finger 25 than the fifth region 29. The seventh region 31 includes the sixth region 30 and extends in the second arrangement direction DL2. The eighth region 32 includes the fifth region 29 and extends in the second arrangement direction DL2.

[0033] The difference between the sound speed in the seventh region 31 and the sound speed in the eighth region 32 is defined as a second sound speed difference.

[0034] When the speed of sound in the seventh region 31 is not constant with respect to the position in the seventh region 31, the speed of sound in the seventh region 31 may be any of the average value, the maximum value, the minimum value, and any other representative value of the multiple speeds of sound in the seventh region 31. When the speed of sound in the eighth region 32 is not constant with respect to the position in the eighth region 32, the speed of sound in the 8th region 32 may be any of the average value, the maximum value, the minimum value, and any other representative value of the multiple speeds of sound in the 8th region 32.

[0035] In filter 101, the first sound velocity difference is larger than the second sound velocity difference. Filter 101 can reduce the risk that spurious signals resulting from fifth region 29 and tip 33 of fourth electrode finger 26 will occur within the passband of filter 101. Filter 101 can reduce the disadvantages of the resonator used in the configuration of filter 101. As a result, filter 101 with improved frequency characteristics can be realized.

[0036] 1, the filter 101 may include a plurality of parallel arm resonators KP and a plurality of series arm resonators KS. In this case, the minimum value of the first sound velocity difference among the plurality of parallel arm resonators KP may be greater than the maximum value of the second sound velocity difference among the plurality of series arm resonators KS.

[0037] The cross-sectional area of ​​the first region 12 cut along the first arrangement direction DL1 in a plan view of the filter 101 may be larger than the cross-sectional area of ​​the second region 13 cut along the first arrangement direction DL1 in a plan view of the filter 101. This makes it easy to increase the first sound speed difference.

[0038] The duty of the first electrode finger 8 and the second electrode finger 9 is a first value in the portion where the first region 12 faces the tip 16 of the second electrode finger 9, and a second value is a maximum value in the portion where the second region 13 faces the second electrode finger 9. The duty of the first electrode finger 8 and the second electrode finger 9 can be defined as a ratio of the sum of the width of the first electrode finger 8 and the width of the second electrode finger 9 to twice the pitch p1 of the first electrode finger 8 and the second electrode finger 9. The pitch p1 can be defined as the distance between the center 35 of the first electrode finger 8 and the center 36 of the second electrode finger 9 in the first arrangement direction DL1. The pitch means the center-to-center distance, and can also be said to mean the repetition interval. The first value may be larger than the second value. This makes it easy to increase the first sound velocity difference.

[0039] The difference between the first value and the second value may be equal to or greater than 0.05 and equal to or less than 0.2, which makes it easy to increase the first sound speed difference.

[0040] The duty of the third electrode finger 25 and the fourth electrode finger 26 is a third value in the portion where the fifth region 29 faces the tip 33 of the fourth electrode finger 26, and the maximum value is a fourth value in the portion where the sixth region 30 faces the fourth electrode finger 26. The duty of the third electrode finger 25 and the fourth electrode finger 26 can be defined as a ratio of the sum of the width of the third electrode finger 25 and the width of the fourth electrode finger 26 to twice the pitch p2 of the third electrode finger 25 and the fourth electrode finger 26. The pitch p2 can be defined as the distance between the center 37 of the third electrode finger 25 and the center 38 of the fourth electrode finger 26 in the second arrangement direction DL2. The difference between the third value and the fourth value may be 0.2 or less. This can reduce the risk that the second sound speed difference becomes too large.

[0041] The width W12 of the first region 12 along the first arrangement direction DL1 may be greater than the width W13 of the second region 13 along the first arrangement direction DL1, which makes it easy to increase the first sound speed difference.

[0042] In the filter 101, the parallel arm resonator KP may have a first dielectric layer 3 located above the first IDT electrode 2, and the series arm resonator KS may have a second dielectric layer 20 located above the second IDT electrode 19. In this case, the mass of the first dielectric layer 3 may be greater than the mass of the second dielectric layer 20. This makes it easy to make the first sound velocity difference greater than the second sound velocity difference. The thickness of the first dielectric layer 3 may be greater than the thickness of the second dielectric layer 20, the volume of the first dielectric layer 3 may be greater than the volume of the second dielectric layer 20, the density of the first dielectric layer 3 may be greater than the density of the second dielectric layer 20, or two or more of these may be applied.

[0043] The length L1 of the opposing portion between the first region 12 and the tip 16 of the second electrode finger 9 in the first direction D1 may be equal to or greater than the pitch p1 of the first electrode fingers 8 and the second electrode fingers 9, and may be equal to or less than 2.5 times the pitch p1. If the length L1 is less than the pitch p1, the reduction in the transverse mode spurious may be insufficient. If the length L1 is more than 2.5 times the pitch p1, the reduction in the transverse mode spurious may be insufficient.

[0044] The first IDT electrode 2 may have a first bus bar 10 electrically connected to the first electrode finger 8, and dummy electrode fingers 39 extending in the first direction D1 from the first bus bar 10 and facing the second electrode fingers 9 in the first direction D1. The dummy electrode fingers 39 may have a function of more precisely controlling the frequency characteristics of the parallel arm resonator KP.

[0045] Length L2 in first direction D1 from tip 40 of dummy electrode finger 39 to region edge 41, which is the end of first region 12 on the second region 13 side, may be 1.5 times or more and 2.5 times or less than pitch p1 of first electrode fingers 8 and second electrode fingers 9. If length L2 is less than 1.5 times pitch p1, reduction in transverse mode spurious emissions may be insufficient. If length L2 is more than 2.5 times pitch p1, reduction in transverse mode spurious emissions may be insufficient.

[0046] The cross-sectional area of ​​the dummy electrode fingers 39 cut along the first arrangement direction DL1 in a plan view of the filter 101 may be larger than the cross-sectional area of ​​the second region 13 cut along the first arrangement direction DL1 in a plan view of the filter 101. This makes it easy to increase the first sound velocity difference.

[0047] The second sound speed difference may be 0. That is, the sound speed in the seventh region 31 may be equal to the sound speed in the eighth region 32. In this case, it is easy to make the first sound speed difference larger than the second sound speed difference.

[0048] Spurious emissions caused by the fifth region 29 and the tip portion 33 of the fourth electrode finger 26 may not occur within the passband of the filter 101. This can reduce the disadvantages of the resonators used in the configuration of the filter 101. Specifically, the spurious emissions are thought to occur as low-frequency resonance caused by the difference in sound speed between the fifth region 29 and the tip portion 33 and the seventh region 31. The passband of the filter 101 may be determined in the specifications by the manufacturer of the filter 101, for example.

[0049] The thickness T1 of the first piezoelectric portion 1 and the thickness T18 of the second piezoelectric portion 18 may be the same.

[0050] At least one of the parallel arm resonator KP and the series arm resonator KS may excite an antisymmetric A1 mode. At least one of the parallel arm resonator KP and the series arm resonator KS may excite a bulk wave. At least one of the vibration mode of the parallel arm resonator KP that excites a bulk wave and the vibration mode of the series arm resonator KS that excites a bulk wave may be a thickness shear mode. The parallel arm resonator KP may not have the first multilayer reflective film 4. The series arm resonator KS may not have the second multilayer reflective film 21.

[0051] The first piezoelectric body may be provided with both the first piezoelectric body portion 1 and the second piezoelectric body portion 18. In other words, the first piezoelectric body portion 1 and the second piezoelectric body portion 18 may be provided on the same piezoelectric body. The first piezoelectric body may be provided with the first piezoelectric body portion 1, and the second piezoelectric body may be provided with the second piezoelectric body portion 18. In other words, the first piezoelectric body portion 1 and the second piezoelectric body portion 18 may be provided on separate piezoelectric bodies.

[0052] As a method for changing the cross-sectional area when first electrode fingers 8 are cut along first arrangement direction DL1 in a plan view of filter 101, at least one of the following (1) and (2) may be implemented.

[0053] (1) The duty of first electrode finger 8 and second electrode finger 9 may be changed. For example, the duty of first electrode finger 8 and second electrode finger 9 in the portion where first region 12 and tip portion 16 face each other may be made larger than the duty of first electrode finger 8 and second electrode finger 9 in the portion where second region 13 and second electrode finger 9 face each other.

[0054] (2) The thickness of first electrode fingers 8 may be changed. For example, the thickness of first region 12 may be made larger than the thickness of second region 13.

[0055] If necessary, the width W12 of the first region 12 along the first arrangement direction DL1 may be equal to or smaller than the width W13 of the second region 13 along the first arrangement direction DL1. The width of the fifth region 29 along the second arrangement direction DL2 may be greater than the width of the sixth region 30 along the second arrangement direction DL2, or may be equal to or smaller than the width of the sixth region 30 along the second arrangement direction DL2. The magnitude relationship between the width W12 and the width W13 may be appropriately set according to a target value of the first sound speed difference. The magnitude relationship between the widths of the fifth region 29 and the sixth region 30 may be appropriately set according to a target value of the second sound speed difference.

[0056] Although various methods for making the first sound velocity difference larger than the second sound velocity difference have been described above, a combination of multiple methods may be used. For example, the first value may be larger than the second value, and the mass of the first dielectric layer 3 may be larger than the mass of the second dielectric layer 20.

[0057] In the parallel arm resonator KP shown in FIGS. 2 and 3, if the sound velocity in the fourth region 15 is made smaller than the sound velocity in the third region 14 in order to increase the first sound velocity difference, spurious components may occur at frequencies lower than the resonant frequency.

[0058] Fig. 6 is a graph showing an example of the relationship between impedance and frequency in the parallel arm resonator KP shown in Fig. 2 and Fig. 3. Graph 1001 in Fig. 6 shows actual measured values ​​of the absolute value of impedance with respect to frequency and actual measured values ​​of the phase of impedance with respect to frequency. Graph 1002 in Fig. 6 shows simulated values ​​of the absolute value of impedance with respect to frequency.

[0059] Xb = Xa + 400 Xc = Xa + 800 Xd = Xa + 1200 Xe = Xa + 1600 The frequency notation in Fig. 6 is defined as above. According to Fig. 6, a spurious response 43 occurs in a frequency range 42 between the frequency at which the absolute value of the impedance in the third region 14 is smallest and the frequency at which the absolute value of the impedance in the fourth region 15 is smallest. It can be seen that the frequency at which the spurious response 43 occurs can be predicted to some extent depending on the sound speed in the third region 14 and the sound speed in the fourth region 15.

[0060] In the following, a description will be given with reference to examples and comparative examples. In this description, for convenience, a resonator having the configuration shown in Figures 2 and 3 will be referred to as a "first resonator," and a resonator having the configuration shown in Figures 4 and 5 will be referred to as a "second resonator."

[0061] The embodiment is a filter 101 in which the parallel arm resonators KP1 to KP3 are each a first resonator, and the series arm resonators KS1 to KS4 are each a second resonator.

[0062] The comparative example is a filter 101 in which the parallel arm resonators KP1 to KP3 are each a first resonator, the series arm resonators KS1 and KS4 are each a first resonator, and the series arm resonators KS2 and KS3 are each a second resonator.

[0063] 7 and 8 are graphs showing the relationship of the transmission characteristics to the frequency for the example and the comparative example, respectively.

[0064] X2=X1+2000 X3=X1+4000 X4=X1+1000 X5=X1+1200 X6=X1+1400 X7=X1+1600 The frequency notations in Figures 7 and 8 are defined as above.

[0065] 7 and 8, it can be seen that the embodiment has better frequency characteristics than the comparative example, particularly when paying attention to the characteristics indicated by the arrow 44 in Fig. 8. If the first resonator has a resonant frequency within the passband of the filter 101, the frequency characteristics within the passband of the filter 101 may be poor. Therefore, it can be seen that only the resonator having no resonant frequency within the passband of the filter 101 may be the first resonator.

[0066] Fig. 9 is a graph showing the relationship of impedance phase to frequency for an example. Fig. 10 is a graph showing the relationship of impedance phase to frequency for a comparative example. In Figs. 9 and 10, the solid line shows the characteristics of the first resonator, and the dashed line shows the characteristics of the second resonator.

[0067] 9 and 10 are compared. In the comparative example, a ripple 45 occurs in the characteristics of the first resonator. In the example, no characteristics corresponding to the ripple 45 are found. It can be seen that this ripple 45 is one of the reasons why the example has better frequency characteristics than the comparative example.

[0068] [Embodiment 2] Fig. 11 is a cross-sectional view showing a schematic configuration of a resonator K according to embodiment 2 of the present disclosure. As shown in Fig. 11, the resonator K may have a membrane structure. The resonator K may be a parallel arm resonator KP or a series arm resonator KS.

[0069] That is, the following can be said. At least one of the parallel arm resonators KP and the series arm resonators KS may have a membrane structure. At least one of the parallel arm resonators KP1 to KP3 may have a membrane structure. At least one of the series arm resonators KS1 to KS4 may have a membrane structure.

[0070] The resonator K having the membrane structure shown in FIG. 11 does not need to have a multilayer reflective film, and an opening 48 is formed on the piezoelectric body portion 47 side of the support substrate 46, and the piezoelectric body portion 47 is provided so as to cover the opening 48.

[0071] When the resonator K is a parallel arm resonator KP, it may have the following configuration. The support substrate 46 corresponds to the first support substrate 5. The piezoelectric body portion 47 corresponds to the first piezoelectric body portion 1. The dielectric layer 49 corresponds to the first dielectric layer 3. The electrode fingers 50 correspond to the first electrode fingers 8. The bus bar 51 corresponds to the first bus bar 10. The bus bar 52 corresponds to the second bus bar 11.

[0072] When the resonator K is a series arm resonator KS, it may have the following configuration. The support substrate 46 corresponds to the second support substrate 22. The piezoelectric body portion 47 corresponds to the second piezoelectric body portion 18. The dielectric layer 49 corresponds to the second dielectric layer 20. The electrode fingers 50 correspond to the third electrode fingers 25. The bus bar 51 corresponds to the third bus bar 27. The bus bar 52 corresponds to the fourth bus bar 28.

[0073] [Embodiment 3] 12 is a schematic diagram of a communication device 201 according to a third embodiment of the present disclosure. The communication device 201 is an application example of the filter 101, and performs wireless communication using radio waves. The communication device 201 may include a transmission filter 111 and a reception filter 112. Each of the transmission filter 111 and the reception filter 112 may include the filter 101.

[0074] In the communication device 201, a transmission information signal TIS including information to be transmitted may be modulated and frequency-raised (converted into a high-frequency signal having a carrier frequency) by an RF-IC (Radio Frequency-Integrated Circuit) 113, and converted into a transmission signal TS. A band-pass filter 114 may remove unnecessary components from the transmission signal TS that are not in the transmission passband. Next, the transmission signal TS after removing the unnecessary components may be amplified by an amplifier 115 and input to the transmission filter 111.

[0075] The transmission filter 111 may remove unnecessary components outside the transmission passband from the input transmission signal TS. The transmission filter 111 may output the transmission signal TS after removing the unnecessary components to the antenna 116 via the antenna terminal. The antenna 116 may convert the transmission signal TS, which is an electrical signal input thereto, into radio waves as a wireless signal and transmit the radio waves to the outside of the communication device 201.

[0076] Furthermore, the antenna 116 may convert the received radio wave from the outside into a received signal RS, which is an electric signal, and input the received signal RS to the receiving filter 112 via the antenna terminal. The receiving filter 112 may remove unnecessary components outside the receiving passband from the input received signal RS. The receiving filter 112 may output the received signal RS after the unnecessary components have been removed to the amplifier 117. The output received signal RS may be amplified by the amplifier 117. The bandpass filter 118 may remove unnecessary components outside the receiving passband from the amplified received signal RS. The received signal RS after the unnecessary components have been removed may be frequency-downgraded and demodulated by the RF-IC 113, and converted into a received information signal RIS.

[0077] The transmission information signal TIS and the reception information signal RIS may be low-frequency signals (baseband signals) containing appropriate information. For example, the transmission information signal TIS and the reception information signal RIS may be analog voice signals or digitalized voice signals. The passband of the wireless signal may be set appropriately and may conform to various known standards.

[0078] 〔summary〕 A filter according to a first aspect of the present disclosure includes a parallel arm resonator and a series arm resonator. The parallel arm resonator has a first piezoelectric body portion and a first IDT electrode located in a layer higher than the first piezoelectric body portion and including first and second electrode fingers adjacent to each other. The series arm resonator has a second piezoelectric body portion and a second IDT electrode located in a layer higher than the second piezoelectric body portion and including third and fourth electrode fingers adjacent to each other. When an arrangement direction of the first electrode fingers and the second electrode fingers is defined as a first arrangement direction and an arrangement direction of the third electrode fingers and the fourth electrode fingers is defined as a second arrangement direction, the first electrode fingers have a first region facing tips of the second electrode fingers in the first arrangement direction and a second region facing the tips of the first electrode fingers from the first region. the parallel arm resonator includes a third region including the second region and extending in the first arrangement direction, and a fourth region including the first region and extending in the first arrangement direction, the third electrode finger includes a fifth region facing a tip of the fourth electrode finger in the second arrangement direction and a sixth region located closer to the tip of the third electrode finger than the fifth region, and the series arm resonator includes a seventh region including the sixth region and extending in the second arrangement direction, and an eighth region including the fifth region and extending in the second arrangement direction, wherein a first sound velocity difference is a difference between the sound velocity in the third region and the sound velocity in the fourth region, and a second sound velocity difference is a difference between the sound velocity in the seventh region and the sound velocity in the eighth region, the first sound velocity difference is greater than the second sound velocity difference.

[0079] The filter according to a second aspect of the present disclosure is similar to the first aspect, but includes a plurality of the parallel arm resonators and a plurality of the series arm resonators, and a minimum value of the first sound velocity differences among the plurality of parallel arm resonators is greater than a maximum value of the second sound velocity differences among the plurality of series arm resonators.

[0080] The filter according to aspect 3 of the present disclosure is the filter of aspect 1 or 2, wherein the cross-sectional area of ​​the first region when cut along the first arrangement direction in a planar view of the filter is larger than the cross-sectional area of ​​the second region when cut along the first arrangement direction in a planar view of the filter.

[0081] A filter according to aspect 4 of the present disclosure is any one of aspects 1 to 3, wherein the duty of the first electrode finger and the second electrode finger is a first value at a portion where the first region faces the tip of the second electrode finger, and a maximum value is a second value at a portion where the second region faces the second electrode finger, and the first value is greater than the second value.

[0082] A filter according to a fifth aspect of the present disclosure is the filter of the fourth aspect, wherein the difference between the first value and the second value is not less than 0.05 and not more than 0.2.

[0083] The filter according to aspect 6 of the present disclosure, in any one of aspects 1 to 5, has a duty of the third electrode finger and the fourth electrode finger that is a third value at the opposing portion between the fifth region and the tip of the fourth electrode finger, and a fourth value at the opposing portion between the sixth region and the fourth electrode finger, and the difference between the third value and the fourth value is 0.2 or less.

[0084] A filter according to a seventh aspect of the present disclosure is the filter of any one of the first to sixth aspects, wherein a width of the first region along the first arrangement direction is greater than a width of the second region along the first arrangement direction.

[0085] A filter according to an eighth aspect of the present disclosure is the filter of any one of the first to seventh aspects, wherein the parallel arm resonator has a first dielectric layer located above the first IDT electrode, the series arm resonator has a second dielectric layer located above the second IDT electrode, and the mass of the first dielectric layer is greater than the mass of the second dielectric layer.

[0086] The filter according to aspect 9 of the present disclosure, in any one of aspects 1 to 8, has a length of an opposing portion between the first region and the tip of the second electrode finger in the longitudinal direction of the first electrode finger that is greater than or equal to the pitch of the first electrode finger and the second electrode finger and is less than or equal to 2.5 times the pitch.

[0087] A filter according to aspect 10 of the present disclosure is any one of aspects 1 to 9, wherein the first IDT electrode has a bus bar electrically connected to the first electrode finger, and a dummy electrode finger extending from the bus bar in the longitudinal direction of the first electrode finger and facing the second electrode finger in the longitudinal direction of the first electrode finger.

[0088] The filter according to aspect 11 of the present disclosure is, in aspect 10, such that the length in the longitudinal direction of the first electrode finger from the tip of the dummy electrode finger to the end of the first region on the second region side is greater than or equal to 1.5 times the pitch of the first electrode fingers and the second electrode fingers and is less than or equal to 2.5 times the pitch.

[0089] A filter according to aspect 12 of the present disclosure is such that, in aspect 10 or 11, the cross-sectional area of ​​the dummy electrode fingers cut along the first arrangement direction in a planar view of the filter is larger than the cross-sectional area of ​​the second region cut along the first arrangement direction in a planar view of the filter.

[0090] A thirteenth aspect of the present disclosure relates to the filter of any one of the first to twelfth aspects, wherein the second sound velocity difference is zero.

[0091] The filter according to a fourteenth aspect of the present disclosure is any one of the first to thirteenth aspects, in which spurious emissions caused by the fifth region and the tips of the fourth electrode fingers do not occur within the passband of the filter.

[0092] A filter according to a fifteenth aspect of the present disclosure is the filter of any one of the first to fourteenth aspects, wherein the first piezoelectric portion and the second piezoelectric portion have the same thickness.

[0093] A filter according to a sixteenth aspect of the present disclosure is the filter of any one of the first to fifteenth aspects, in which at least one of the parallel arm resonator and the series arm resonator excites an A1 mode, which is an antisymmetric mode.

[0094] A filter according to a seventeenth aspect of the present disclosure is the filter of any one of the first to sixteenth aspects, wherein at least one of the parallel arm resonator and the series arm resonator excites a bulk wave.

[0095] A filter according to an eighteenth aspect of the present disclosure is the filter of any one of the first to seventeenth aspects, wherein at least one of the parallel arm resonator and the series arm resonator has a multilayer reflective film structure or a membrane structure.

[0096] A communication device according to a nineteenth aspect of the present disclosure includes a filter according to any one of the first to eighteenth aspects.

[0097] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. [Explanation of symbols]

[0098] 1 First piezoelectric body 2 1st IDT electrode 3 First Dielectric Layer 4 1st multilayer reflective film 5 First support board 6. First low acoustic impedance layer 7 First high acoustic impedance layer 8 1st electrode finger 9 Second electrode finger 10 First bus bar 11 Second bus bar 12 First area 13 Second area 14 Third area 15 4th area 16 Tip of second electrode finger 17 Tip of first electrode finger 18 Second piezoelectric body 19 2nd IDT electrode 20 Second dielectric layer 21 2nd multilayer reflective film 22 Second support board 23 Second low acoustic impedance layer 24 Second high acoustic impedance layer 25 3rd electrode finger 26 4th electrode finger 27 3rd bus bar 28 4th bus bar 29 5th area 30 Area 6 31 Area 7 32 Area 8 33 Tip of fourth electrode finger 34 Tip of third electrode finger 35 Center of first electrode finger 36 Center of second electrode finger 37 Center of third electrode finger 38 Center of fourth electrode finger 39 Dummy electrode finger 40 Tip of dummy electrode finger 41 Area edge 46 Support substrate 47 Piezoelectric part 48 Opening 49 Dielectric Layer 50 electrode fingers 51 Busbar 52 Busbar 101 Filters 201 Communication equipment D1 1st direction D2 2nd direction D3 Third direction D4 4th direction DL1 1st array direction DL2 Second array direction K resonator KP, KP1~KP3 parallel arm resonator KS, KS1 to KS4 series arm resonators L1: The length of the opposing portion between the first region and the tip of the second electrode finger in the first direction L2: Length in the first direction from the tip of the dummy electrode finger to the end of the first region on the second region side p1 Pitch of the first and second electrode fingers p2 Pitch of the third and fourth electrode fingers T1 Thickness of the first piezoelectric part T18 Thickness of the second piezoelectric part W12 Width of the first region along the first array direction W13 Width of the second region along the first array direction

Claims

1. The resonator includes a parallel arm resonator and a series arm resonator, The parallel arm resonator includes: A first piezoelectric portion; a first IDT electrode located in a layer above the first piezoelectric portion and including first and second electrode fingers adjacent to each other; The series arm resonator includes: A second piezoelectric portion; a second IDT electrode located in a layer above the second piezoelectric portion and including third and fourth electrode fingers adjacent to each other, When the arrangement direction of the first electrode fingers and the second electrode fingers is defined as a first arrangement direction, and the arrangement direction of the third electrode fingers and the fourth electrode fingers is defined as a second arrangement direction, the first electrode finger includes a first region facing a tip portion of the second electrode finger in the first arrangement direction, and a second region located closer to the tip portion of the first electrode finger than the first region, the parallel arm resonator includes a third region including the second region and extending in the first arrangement direction, and a fourth region including the first region and extending in the first arrangement direction, the third electrode finger includes a fifth region facing a tip of the fourth electrode finger in the second arrangement direction, and a sixth region located closer to the tip of the third electrode finger than the fifth region, the series arm resonator includes a seventh region which includes the sixth region and extends in the second arrangement direction, and an eighth region which includes the fifth region and extends in the second arrangement direction, A filter, wherein a difference between the sound speed in the third region and the sound speed in the fourth region is a first sound speed difference, and a difference between the sound speed in the seventh region and the sound speed in the eighth region is a second sound speed difference, the first sound speed difference being greater than the second sound speed difference.

2. the parallel arm resonators and the series arm resonators are each provided in a plurality of numbers, 2. The filter according to claim 1, wherein a minimum value of the first sound velocity differences among the parallel arm resonators is greater than a maximum value of the second sound velocity differences among the series arm resonators.

3. 2. The filter according to claim 1, wherein a cross-sectional area of ​​the first region cut along the first arrangement direction in a planar view of the filter is larger than a cross-sectional area of ​​the second region cut along the first arrangement direction in a planar view of the filter.

4. a duty of the first electrode finger and the second electrode finger is a first value at a portion where the first region and a tip of the second electrode finger face each other, and a maximum duty of the duty of the first electrode finger and the second electrode finger is a second value at a portion where the second region and the second electrode finger face each other, The filter of claim 1 , wherein the first value is greater than the second value.

5. The filter of claim 4 , wherein the difference between the first value and the second value is greater than or equal to 0.05 and less than or equal to 0.

2.

6. a duty of the third electrode finger and the fourth electrode finger is a third value in a portion where the fifth region and a tip of the fourth electrode finger face each other, and a maximum duty of the duty of the third electrode finger and the fourth electrode finger is a fourth value in a portion where the sixth region and the fourth electrode finger face each other, The filter of claim 1 , wherein the difference between the third value and the fourth value is less than or equal to 0.

2.

7. The filter of claim 1 , wherein a width of the first region along the first arrangement direction is greater than a width of the second region along the first arrangement direction.

8. the parallel arm resonator has a first dielectric layer located above the first IDT electrode, the series arm resonator has a second dielectric layer located above the second IDT electrode, The filter of claim 1 , wherein the mass of the first dielectric layer is greater than the mass of the second dielectric layer.

9. 2. The filter according to claim 1, wherein a length of an opposing portion between the first region and the tip of the second electrode finger in the longitudinal direction of the first electrode finger is equal to or greater than the pitch of the first electrode finger and the second electrode finger and is equal to or less than 2.5 times the pitch.

10. The first IDT electrode is a bus bar electrically connected to the first electrode finger; 2. The filter according to claim 1, further comprising: a dummy electrode finger extending from the bus bar in a longitudinal direction of the first electrode finger and facing the second electrode finger in the longitudinal direction of the first electrode finger.

11. 11. The filter according to claim 10, wherein a length from a tip of the dummy electrode finger to an end of the first region on the second region side in a longitudinal direction of the first electrode finger is 1.5 times or more the pitch of the first electrode fingers and the second electrode fingers and is 2.5 times or less the pitch.

12. The filter according to claim 10, wherein a cross-sectional area of ​​the dummy electrode fingers cut along the first arrangement direction in a planar view of the filter is larger than a cross-sectional area of ​​the second region cut along the first arrangement direction in a planar view of the filter.

13. The filter of claim 1 , wherein the second sound speed difference is zero.

14. 2. The filter according to claim 1, wherein spurious components resulting from said fifth region and the tips of said fourth electrode fingers do not occur within a passband of said filter.

15. The filter according to claim 1 , wherein a thickness of the first piezoelectric portion is the same as a thickness of the second piezoelectric portion.

16. At least one of the parallel arm resonator and the series arm resonator is an antisymmetric mode A １ 2. The filter of claim 1, which excites a mode.

17. The filter according to claim 1 , wherein at least one of the parallel arm resonator and the series arm resonator excites a bulk wave.

18. 2. The filter according to claim 1, wherein at least one of the parallel arm resonator and the series arm resonator has a multilayer reflective film structure or a membrane structure.

19. A communication device comprising a filter according to any one of claims 1 to 18.

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