Elastic wave device

Abstract

Provided is an elastic wave device having an elastic wave resonator and a longitudinal coupling type elastic wave resonator filter, which can more effectively suppress a lateral mode. An elastic wave device (1) has an elastic wave resonator (5) and a longitudinal coupling type elastic wave resonator filter (6), and the length of the first and second edge regions (C1, C2) in the IDT electrode, which is the dimension in the direction in which the electrode fingers (21, 22) extend, is set shorter in the longitudinal coupling type elastic wave resonator filter (6) than in the elastic wave resonator (5).

Description

TECHNICAL FIELD

[0001] The present application relates to an elastic wave device having a configuration in which first and second edge regions as low-velocity regions are provided at both ends in a cross region. BACKGROUND

[0002] In the elastic wave device described in Patent Document 1 below, a piston mode is formed so that suppression of a transverse mode is achieved. More specifically, in the IDT electrode, a region in which adjacent electrode fingers overlap in the elastic wave propagation direction is set as a cross region. The cross region has a central region and first and second edge regions disposed outside the direction in which the electrode fingers of the central region extend. The first and second edge regions are made to have a lower velocity than the velocity in the central region. Moreover, regions having a higher velocity than the central region are provided outside the first and second edge regions. Thus, a piston mode is formed.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENT

[0005] Patent Document 1: Japanese Patent No. 5503020 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the elastic wave device described in Patent Document 1, by forming a piston mode, suppression of a transverse mode is achieved.

[0008] However, in an elastic wave device having an elastic wave resonator and a longitudinal-coupling-type elastic wave resonator filter, in a case where the first and second edge regions are provided in both the elastic wave resonator and the longitudinal-coupling-type elastic wave resonator filter, sometimes the transverse mode cannot be sufficiently suppressed.

[0009] An object of the present application is to provide an elastic wave device having an elastic wave resonator and a longitudinal-coupling-type elastic wave resonator filter, which can more effectively suppress a transverse mode.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] The elastic wave device according to the present application includes an elastic wave resonator including an IDT electrode formed on a first piezoelectric substrate, and a longitudinal coupling type elastic wave resonator filter including a plurality of IDT electrodes formed on a second piezoelectric substrate, each of the IDT electrodes of the elastic wave resonator and the IDT electrodes of the longitudinal coupling type elastic wave resonator filter has a plurality of electrode fingers, and has a crossing region in which the electrode fingers cross each other in an elastic wave propagation direction, the crossing region has a central region, and first and second edge regions provided on both outer sides of the central region in a direction in which the electrode fingers extend and have a lower acoustic velocity than the central region, and first and second gap regions provided outside the direction in which the electrode fingers of the first and second edge regions extend and have a higher acoustic velocity than the central region, and a length of the first and second edge regions in the longitudinal coupling type elastic wave resonator filter is shorter than a length of the first and second edge regions in the elastic wave resonator.

[0012] Effects of the Invention

[0013] According to the elastic wave device according to the present application, the transverse mode can be effectively suppressed in either the elastic wave resonator or the longitudinal coupling type elastic wave resonator filter. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 FIG. 1 is a circuit diagram of an elastic wave device according to a first embodiment of the present application.

[0015] Figure 2 FIG. 2 is a front sectional view for explaining a configuration of an elastic wave resonator in the elastic wave device according to the first embodiment of the present application.

[0016] Figure 3 FIG. 3 is a schematic plan view for explaining an electrode arrangement of the elastic wave resonator in the elastic wave device according to the first embodiment of the present application.

[0017] Figure 4 FIG. 4 is a plan view showing an IDT electrode of the elastic wave resonator in the elastic wave device according to the first embodiment of the present application.

[0018] Figure 5 FIG. 5 is a partially cutaway plan view showing a main portion of the IDT electrode shown in FIG. 4 in an enlarged manner. Figure 4

[0019] Figure 6 FIG. 6 is a schematic plan view for explaining an electrode arrangement of a longitudinal coupling type elastic wave resonator filter in the elastic wave device according to the first embodiment of the present application.

[0020] FIG. 7 is a plan view showing an IDT electrode of the longitudinal coupling type elastic wave resonator filter in the elastic wave device according to the first embodiment of the present application.Figure 7 (a) and Figure 7 (b) is a top view showing the main part of the IDT electrode of the elastic wave resonator of the elastic wave device according to the first embodiment and the main part of the IDT electrode of the longitudinally coupled elastic wave resonator filter.

[0021] Figure 8 (a) is a graph showing the impedance characteristics of the elastic wave resonator in the elastic wave device according to the first embodiment. Figure 8 (b) is a diagram showing the characteristics of S11.

[0022] Figure 9 This is a graph showing the relationship between the lengths of the first and second edge regions of the elastic wave resonator in the elastic wave device according to Embodiment 1 and the intensity of the transverse mode ripple, i.e., the ripple intensity.

[0023] Figure 10 This is a graph showing the relationship between the lengths of the first and second edge regions of the longitudinally coupled elastic wave resonator filter in Embodiment 1 and the intensity of the transverse mode ripple, i.e., the ripple intensity.

[0024] Figure 11 This is a graph showing the relationship between the lengths of the first and second edge regions of the elastic wave resonator in the elastic wave device of Example 2, which uses a LiNbO3 film, and the intensity of the transverse mode ripple, i.e., the ripple intensity.

[0025] Figure 12 This is a graph showing the relationship between the lengths of the first and second edge regions and the intensity of the transverse mode ripple, i.e., the ripple intensity, in Example 2 using a LiNbO3 film.

[0026] Figure 13 This is a circuit diagram of the elastic wave device according to the second embodiment of the present invention.

[0027] Figure 14 This is a top view illustrating a modified example of the IDT electrode in the elastic wave device according to the second embodiment of the present invention.

[0028] Figure 15 This is a top view illustrating another variation of the IDT electrode in the elastic wave device according to the second embodiment of the present invention. Detailed Implementation

[0029] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0030] In addition, it should be noted that the embodiments described in this specification are illustrative, and structural substitutions or combinations can be made between different embodiments.

[0031] Figure 1 This is a circuit diagram of the elastic wave device according to the first embodiment of the present invention.

[0032] The elastic wave device 1 is a duplexer, comprising a receiving filter 2 and a transmitting filter 3. One end of the receiving filter 2 and the transmitting filter 3 are connected to the antenna terminal 4. The receiving filter 2 and the transmitting filter 3 are both elastic wave filters. In the receiving filter 2, a single-port elastic wave resonator 5 is connected in series with a longitudinally coupled elastic wave resonator filter 6. The transmitting filter 3 has multiple series-arm resonators S1-S3 and multiple parallel-arm resonators P1 and P2. The series-arm resonators S1-S3 and the parallel-arm resonators P1 and P2 are each composed of a single-port elastic wave resonator. That is, the transmitting filter 3 is a trapezoidal filter with multiple elastic wave resonators.

[0033] In the elastic wave resonator 5 of the receiving filter 2 and the longitudinally coupled elastic wave resonator filter 6, first and second edge regions are provided in the intersection region of the IDT electrodes to form a piston mode. The lengths of the first and second edge regions are different in the elastic wave resonator 5 and the longitudinally coupled elastic wave resonator filter 6. As a result, transverse modes can be suppressed more effectively. The construction of the elastic wave resonator 5 and the longitudinally coupled elastic wave resonator filter 6 will be described in more detail below.

[0034] Figure 2 This is a front sectional view used to illustrate the structure of the elastic wave resonator 5. In the elastic wave resonator 5, an IDT electrode 16 and reflectors 17 and 18 are provided on the first piezoelectric substrate 15. Figure 3 This is a schematic top view showing the portion where the IDT electrode 16 and reflectors 17 and 18 are provided. Reflectors 17 and 18 are provided on both sides of the elastic wave propagation direction of the IDT electrode 16, thereby forming a single-port elastic wave resonator.

[0035] In addition, such as Figure 2 As shown, in the first piezoelectric substrate 15, a support substrate 11, a high-velocity film 12 as a high-velocity material layer, a low-velocity film 13 as a low-velocity material layer, and a piezoelectric film 14 are sequentially stacked. An IDT electrode 16 is stacked on the piezoelectric film 14. In the first embodiment, the piezoelectric film 14 is composed of a lithium tantalate single crystal film.

[0036] The support substrate 11 is made of semiconductors such as Si and SiC, or insulators such as alumina and quartz. The material of the support substrate 11 is not particularly limited.

[0037] The high-velocity membrane 12 is made of a high-velocity material. Furthermore, the low-velocity membrane 13 is made of a low-velocity material.

[0038] The high-velocity material is a material in which the velocity of a bulk wave propagating therein is higher than the velocity of the elastic wave propagating in the piezoelectric film 14. As such a high-velocity material, various materials such as alumina, silicon carbide, silicon nitride, silicon oxynitride, silicon, sapphire, lithium tantalate, lithium niobate, quartz, bauxite, zirconia, cordierite, mullite, block talc, forsterite, magnesium oxide, a DLC (diamond-like carbon) film, a medium having the above-mentioned material as a main component, a medium having a mixture of the above-mentioned materials as a main component, and the like can be used.

[0039] The low-velocity material is a material in which the velocity of a bulk wave propagating therein is lower than the velocity of the bulk wave propagating in the piezoelectric film 14. As such a low-velocity material, various materials such as silicon oxide, glass, silicon oxynitride, tantalum oxide, a compound in which fluorine, carbon, boron, hydrogen, or a silanol group is added to silicon oxide, a medium having the above-mentioned material as a main component, and the like can be used.

[0040] Further, the high-velocity material layer can also function as a support substrate.

[0041] Figure 4 is a plan view showing the IDT electrode 16 of the elastic wave resonator 5, Figure 5 is a partially cutaway plan view showing a main portion of Figure 4 . The IDT electrode 16 has a plurality of first electrode fingers 21 and a plurality of second electrode fingers 22. The plurality of first electrode fingers 21 and the plurality of second electrode fingers 22 are alternately and oppositely arranged. The base end of the first electrode finger 21 is connected to a first bus bar 23. The first bus bar 23 has a plurality of opening portions 23c arranged along the direction in which the elastic wave propagates. The portion of the first bus bar 23 on the side of the intersection region described later than the opening portions 23c is an inner bus bar portion 23a. The region on the side of the intersection width direction of the opening portions 23c is an outer bus bar portion 23b. A linking portion 23d is provided at a portion where the first electrode finger 21 is extended. The linking portion 23d links the inner bus bar portion 23a and the outer bus bar portion 23b.

[0042] The base end of the second electrode finger 22 is connected to a second bus bar 24. The second bus bar 24 is configured similarly to the first bus bar 23. That is, the second bus bar 24 has an inner bus bar portion 24a, an outer bus bar portion 24b, a plurality of opening portions 24c, and a plurality of linking portions 24d.

[0043] Further, the inner bus bar portions 23a, 24a, the outer bus bar portions 23b, 24b, and the opening portions 23c, 24c can not be formed in the first bus bar 23 and the second bus bar 24.

[0044] The region where the first electrode finger 21 and the second electrode finger 22 overlap in the direction of elastic wave propagation is called the intersection region A. The intersection region A has a central region B and first and second edge regions C1 and C2 located outside the direction in which the first and second electrode fingers 21 and 22 extend from the central region B. In the first and second edge regions C1 and C2, wide portions 25 and 26 are provided on the first electrode finger 21 and the second electrode finger 22. That is, the width of the first and second electrode fingers 21 and 22 in the first and second edge regions C1 and C2 is larger than the width of the first and second electrode fingers 21 and 22 in the central region B. Furthermore, the width of an electrode finger refers to the dimension in a direction orthogonal to the direction in which the first and second electrode fingers 21 and 22 extend.

[0045] Here, the dimensions of the first and second edge regions C1 and C2 in the direction extending from the first and second electrode fingers 21 and 22 are defined as the length X of the first and second edge regions C1 and C2. The wide portions 25 and 26 are provided extending over this length X.

[0046] On the other hand, due to the presence of the aforementioned wide portions 25 and 26, the sound velocity in the first and second edge regions C1 and C2 is lower than that in the central region B. Furthermore, first and second gap regions G1 and G2 are provided outside the direction of the extension of the first and second electrode fingers 21 and 22 in the first and second edge regions C1 and C2.

[0047] The sound velocity in the regions of the first and second gap regions G1 and G2, and the regions of the first and second busbars 23 and 24 with openings 23c and 24c, is higher than the sound velocity in the first and second edge regions C1 and C2. Therefore, a piston mode can be formed, which can suppress transverse mode ripple. Alternatively, the openings 23c and 24c of the first and second busbars 23 and 24 may not be provided. If the sound velocity in the first and second gap regions G1 and G2 is higher than the sound velocity in the first and second edge regions C1 and C2, a piston mode can be formed.

[0048] Reference Figure 4 as well as Figure 5 The construction of the IDT electrode 16 of the elastic wave resonator 5 has been described, but... Figure 1 The IDT electrodes of the longitudinally coupled elastic wave resonator filter 6 shown also have the same construction. Figure 6 This is a schematic top view showing the portion of the longitudinally coupled elastic wave resonator filter 6 with multiple IDT electrodes. The electrodes are disposed on the first piezoelectric substrate, which also serves as the second piezoelectric substrate. Figure 6The electrode configuration shown constitutes a longitudinally coupled elastic wave resonator filter 6. Alternatively, the longitudinally coupled elastic wave resonator filter 6 may be constructed on a second piezoelectric substrate, different from the first piezoelectric substrate, instead of the first. In the longitudinally coupled elastic wave resonator filter 6, multiple IDT electrodes 6a to 6c are arranged along the elastic wave propagation direction. Reflectors 6d and 6e are arranged outside the elastic wave propagation direction in the region where the IDT electrodes 6a to 6c are located. The number of IDT electrodes 6a to 6c is not particularly limited.

[0049] In the multiple IDT electrodes 6a to 6c of the longitudinally coupled elastic wave resonator filter 6, also with Figure 4 as well as Figure 5 Similarly, the IDT electrode 16 shown has a central region B and first and second edge regions C1 and C2 in the cross region A, which forms a piston pattern.

[0050] like Figure 7 (a) and Figure 7 As shown in (b), this embodiment is characterized in that the length X of the first and second edge regions C1 and C2 of the IDT electrodes 6a to 6c in the longitudinally coupled elastic wave resonator filter 6 is shorter than the length X of the first and second edge regions C1 and C2 of the IDT electrodes 16 in the elastic wave resonator 5. Therefore, transverse mode ripple can be effectively suppressed in both the elastic wave resonator 5 and the longitudinally coupled elastic wave resonator filter 6.

[0051] The inventors of this application discovered that in a composite elastic wave device comprising an elastic wave resonator and a longitudinally coupled elastic wave resonator filter, even when transverse mode ripple suppression is achieved by providing the first and second edge regions, transverse mode ripple suppression is sometimes insufficient in both. Furthermore, it was found that the transverse mode ripple suppression effect differs depending on the length of the first and second edge regions in both the elastic wave resonator and the longitudinally coupled elastic wave resonator filter, thus leading to the completion of this invention. (Refer to...) Figures 8-12 Explain it.

[0052] [Example 1]

[0053] As an elastic wave device according to the first embodiment, the elastic wave device of Embodiment 1 was fabricated as follows. The first piezoelectric substrate 15 of the elastic wave resonator 5 and the piezoelectric substrate constituting the longitudinally coupled elastic wave resonator filter 6 are the same piezoelectric substrate. A Si substrate is used as the support substrate 11. A silicon nitride film is used as the high-velocity acoustic film 12. The thickness of the high-velocity acoustic film 12 is set to 900 nm. A silicon oxide film is used as the low-velocity acoustic film 13. The thickness of the low-velocity acoustic film 13 is set to 600 nm.

[0054] A 50° Y-cut X-propagation LiTaO3 film was used as the piezoelectric film 14. The film thickness was set to 600 nm.

[0055] An AlCu film was used as the electrode material constituting the IDT electrode 16 and the reflectors 17, 18. The thickness was set to 100 nm. A Ti layer having a thickness of 12 nm was provided as an adhesion layer between the AlCu film and the piezoelectric film 14. A Ti layer having a thickness of 4 nm was provided as an adhesion layer on the AlCu film. A silicon oxide film was laminated as a protective film on the IDT electrode 16. The thickness of the silicon oxide film was set to 35 nm.

[0056] The duty ratio in the central region B of the IDT electrode 16 was set to 0.45, and the duty ratios in the first and second edge regions Cl, C2 were set to 0.7. The wavelength λ determined by the electrode finger pitch of the IDT electrode 16 was set to 2 μm.

[0057] On the other hand, in the longitudinal coupling type elastic wave resonator filter 6, the IDT electrode and the protective film were also similarly constituted.

[0058] Figure 8 (a) of FIG. 10, Figure 8 (b) of FIG. 10 are graphs showing the impedance characteristics and the S11 characteristics of the elastic wave resonator in the above-described Example 1. In Figure 8 In the S11 characteristics of (b) of FIG. 10, a plurality of ripples indicated by an arrow P appeared.

[0059] The intensity of the largest ripple among the plurality of ripples was set to the ripple intensity.

[0060] Further, in the above-described Example 1, the lengths of the first and second edge regions Cl, C2 were changed in a range of 0.2 λ or more and 1.2 λ or less.

[0061] Figure 9 FIG. 11 is a graph showing the relationship between the lengths of the first and second edge regions Cl, C2 and the ripple intensity in the elastic wave resonator 5. Figure 10 FIG. 12 is a graph showing the relationship between the lengths of the first and second edge regions Cl, C2 and the ripple intensity in the longitudinal coupling type elastic wave resonator filter 6.

[0062] The relationship between the lengths of the first and second edge regions Cl, C2 and the ripple intensity in the longitudinal coupling type elastic wave resonator filter 6 is shown in FIG. 12. Figure 9It is clear that in the elastic wave resonator 5, the length of the first and second edge regions C1, C2 of 0.3λ is most preferable, and the ripple strength is the smallest. Further, it is clear that if the length of the first and second edge regions C1, C2 is 0.2λ or more and 0.5λ or less, the ripple strength can be made to be 1.0 dB or less. On the other hand, it is clear that in the longitudinal coupling type elastic wave resonator filter 6, the ripple strength is the smallest in the case where the length of the first and second edge regions C1, C2 is 0.2λ. Further, it is clear that if the length of the first and second edge regions C1, C2 is 0.15λ or more and 0.25λ or less, the ripple strength can be made to be very small, to be 0.4 dB or less.

[0063] It is clear that if the length X of the first and second edge regions C1, C2 in the longitudinal coupling type elastic wave resonator filter 6 is shorter than the length X of the first and second edge regions C1, C2 in the elastic wave resonator 5, the ripple caused by the lateral mode can be effectively suppressed in both the longitudinal coupling type elastic wave resonator filter 6 and the elastic wave resonator 5. Figure 9 Figure 10 It is clear that if the length X of the first and second edge regions C1, C2 in the longitudinal coupling type elastic wave resonator filter 6 is shorter than the length X of the first and second edge regions C1, C2 in the elastic wave resonator 5, the ripple caused by the lateral mode can be effectively suppressed in both the longitudinal coupling type elastic wave resonator filter 6 and the elastic wave resonator 5.

[0064] As described above, it can be considered that in the longitudinal coupling type elastic wave resonator filter, the lateral mode can be suppressed even if the length of the first and second edge regions is made short, based on the following reasons. In the case of comparing a general elastic wave resonator (single port type resonator) and the longitudinal coupling type elastic wave resonator filter, even if the wavelength in the IDT electrode is the same, since the mode is formed by the reflector in the longitudinal coupling type elastic wave resonator filter, it is possible to make the resonance mode occur on the lower frequency side than in the general elastic wave resonator. Therefore, in the longitudinal coupling type elastic wave resonator filter, the sound velocity in the central region becomes lower than in the general elastic wave resonator, and in conjunction therewith, the sound velocity in the first and second edge regions also becomes lower. In the case where the sound velocity is similarly lowered in the central region and the first and second edge regions of the IDT electrode, the relative sound velocity difference becomes large. Therefore, in the longitudinal coupling type elastic wave resonator filter, the lateral mode can be suppressed even if the length of the first and second edge regions is shorter than in the general elastic wave resonator.

[0065] [Example 2]

[0066] ​In Example 2, 128.5°Y LiNbO3 was used as the piezoelectric film. The thickness was set to 125 nm. An IDT electrode was disposed on the piezoelectric film, with NiCr, Pt, Ti, AlCu, and Ti sequentially stacked from the piezoelectric film side, with thicknesses of 10 nm, 30 nm, 30 nm, 200 nm, and 10 nm respectively. Furthermore, a first protective film composed of SiO2 was disposed to cover the IDT electrode. The film thickness was set to 600 nm. A second protective film of SiN was disposed on top of the first protective film of SiO2. The film thickness was set to 25 nm.

[0067] Figure 11 This is a diagram showing the relationship between the lengths of the first and second edge regions C1 and C2 of the elastic wave resonator 5 in Embodiment 2 and the ripple intensity. Figure 12 This is a diagram showing the relationship between the lengths of the first and second edge regions C1 and C2 and the ripple intensity of the longitudinally coupled elastic wave resonator filter 6 in Embodiment 2.

[0068] Depend on Figure 11 It is clearly known that in the elastic wave resonator 5, the ripple intensity is minimized when the lengths of the first and second edge regions C1 and C2 are 0.3λ. Furthermore, it is known that if the lengths of the first and second edge regions C1 and C2 are greater than 0.25λ and less than 0.35λ, the ripple intensity can be reduced to below 1.0dB. Moreover, from... Figure 12 It is clear that in the longitudinally coupled elastic wave resonator filter 6, the ripple intensity is minimized when the lengths of the first and second edge regions C1 and C2 are 0.15λ. Furthermore, it can be seen that if the lengths of the first and second edge regions C1 and C2 are greater than 0.1λ and less than 0.25λ, the ripple intensity can be made very small, as small as 0.5dB.

[0069] Depend on Figure 11 as well as Figure 12 It is clear that when LiNbO3 is used as the piezoelectric film 14, the ripple intensity in both can be effectively reduced by making the lengths of the first and second edge regions C1 and C2 in the longitudinally coupled elastic wave resonator filter 6 shorter than the lengths of the first and second edge regions C1 and C2 in the elastic wave resonator 5.

[0070] Figure 13 This is a circuit diagram of an elastic wave device according to the second embodiment of the present invention. In the elastic wave device 31, an elastic wave resonator 33 is connected in series with a longitudinally coupled elastic wave resonator filter 32. This elastic wave device 31 is a single bandpass filter. The present invention can also be applied to such a single bandpass filter. That is, the present invention can be widely applied to various elastic wave devices that include an elastic wave resonator and a longitudinally coupled elastic wave resonator filter.

[0071] Further, in the first embodiment, the sound velocity of the first and second edge regions C1, C2 is reduced by providing the wide portion, but as shown in FIG. 6, the mass additional film 25A, 26A can be laminated in the first and second edge regions C1, C2. Figure 14 Figure 14 In this case, the portions shown by the hatching are portions in which the mass additional films 25A, 26A are laminated. By the lamination of the mass additional films 25A, 26A, the sound velocity of the first and second edge regions C1, C2 can be reduced. As the material of such mass additional films 25A, 26A, an insulator such as silicon oxide, silicon nitride oxide, a metal or an alloy such as Ni, W, or the like can be used. Further, the mass additional films 25A, 26A can be provided in a stripe shape along the elastic wave propagation direction so as to reach the region between the adjacent electrode fingers. In this case, as the material of the mass additional films 25A, 26A, an insulating material needs to be used. In addition, in the case where the mass additional films 25A, 26A are provided in the first and second edge regions C1, C2 of the elastic wave resonator 5 and the longitudinal coupling type elastic wave resonator filter 6 to form a piston mode, the thickness of the mass additional films 25A, 26A in the first and second edge regions C1, C2 of the elastic wave resonator 5 and the thickness of the mass additional films 25A, 26A in the first and second edge regions C1, C2 of the longitudinal coupling type elastic wave resonator filter 6 can be the same.

[0072] Further, the mass additional film can be laminated to the side of the electrode finger opposite to the piezoelectric substrate side in the first and second edge regions, or can be laminated between the electrode finger and the piezoelectric substrate. In the case where the mass additional film is laminated between the electrode finger and the piezoelectric substrate, the mass additional film can be extended to reach between the bus bar and the piezoelectric body substrate from the first and second edge regions through the first and second gap regions.

[0073] Further, the mass additional film can be replaced by a dielectric film formed so as to cover the IDT electrode and the piezoelectric substrate. In this case, the thickness of the dielectric film in the first and second edge regions becomes thicker than the thickness of the dielectric film in the central region. By this structure, the sound velocity of the first and second edge regions can be made lower than that of the central region as well.

[0074] Further, as shown in FIG. 7, the mass additional film 25A, 26A can be provided in the first and second edge regions C1, C2 so as to extend to the central region. Figure 15 ​As shown, the high-speed film 27, 28 that increases the speed of sound can also be layered in the central region B of the first and second electrode fingers 21, 22, as shown by the hatched lines. In this case, the high-speed film 27, 28 is not provided in the first and second edge regions Cl, C2. Thus, the speed of sound in the first and second edge regions Cl, C2 can be made relatively low. Note that the high-speed film refers to a film in which the speed of sound of a bulk wave propagating in the high-speed film is faster than the speed of sound of an elastic wave propagating in the piezoelectric film. As the material of the high-speed film 27, 28, Al203, SiN, AlN, or the like can be used. Figure 15 The high-speed film 27, 28 shown is layered on the first and second electrode fingers 21, 22, but can also be provided so as to fill the region between the first and second electrode fingers 21, 22. That is, the high-speed film 27, 28 can be provided so as to extend in the elastic wave propagation direction in the central region B. In this case, the high-speed film 27, 28 can also be integrated. Note that in the case where the high-speed film 27, 28 is provided in the elastic wave resonator 5 and the longitudinal-coupling-type elastic wave resonator filter 6 to form a piston mode, the thickness of the high-speed film 27, 28 in the central region B of the elastic wave resonator 5 and the thickness of the high-speed film 27, 28 in the central region B of the longitudinal-coupling-type elastic wave resonator filter 6 can be the same.

[0075] Further, the high-speed film 27, 28 can also be provided in the first and second edge regions Cl, C2. In this case, the film thickness of the high-speed film 27, 28 in the first and second edge regions Cl, C2 is thinner than the film thickness of the high-speed film 27, 28 in the central region B. With this structure, the speed of sound in the first and second edge regions Cl, C2 can be made lower than the speed of sound in the central region B.

[0076] As described above, in the present application, the structure in which the speed of sound in the first and second edge regions Cl, C2 is made lower than the speed of sound in the central region B is not particularly limited.

[0077] Further, in the piezoelectric substrate described above, the high-speed material layer can also be a support substrate. That is, a support substrate composed of a high-speed material can also be used.

[0078] Further, in the first and second embodiments, an example in which the length of the edge region in the longitudinal-coupling-type elastic wave resonator filter is shorter than the length of the edge region in the elastic wave resonator is shown in the case where the elastic wave resonator and the longitudinal-coupling-type elastic wave resonator filter are connected in series with each other. However, the present application is not limited to this example. For example, the present application can also be applied to Figure 1The transmission filter 3 shown contains at least one elastic wave resonator among the series arm resonators S1 to S3 and the parallel arm resonators P1, P2, and the longitudinal coupling type elastic wave resonator filter 6 contained in the reception filter 2. Specifically, the lengths of the first and second edge regions C1, C2 in the longitudinal coupling type elastic wave resonator filter 6 can also be shorter than the lengths of the first and second edge regions C1, C2 in at least one elastic wave resonator among the series arm resonators S1 to S3 and the parallel arm resonators P1, P2. That is, as long as it is an elastic wave device containing one or more single-port type elastic wave resonators and one or more longitudinal coupling type elastic wave resonator filters, the present application can be applied, and the elastic wave resonators and the longitudinal coupling type elastic wave resonator filters whose lengths of edge regions are changed can be formed anywhere in the elastic wave device.

[0079] Explanation of Reference Signs

[0080] 1... elastic wave device;

[0081] 2... reception filter;

[0082] 3... transmission filter;

[0083] 4... antenna terminal;

[0084] 5... elastic wave resonator;

[0085] 6... longitudinal coupling type elastic wave resonator filter;

[0086] 6a to 6c... IDT electrode;

[0087] 6d, 6e... reflector;

[0088] 11... support substrate;

[0089] 12... high acoustic velocity film;

[0090] 13... low acoustic velocity film;

[0091] 14... piezoelectric film;

[0092] 15... first piezoelectric substrate;

[0093] 16... IDT electrode;

[0094] 17, 18... reflector;

[0095] 21... first electrode finger;

[0096] 22... second electrode finger;

[0097] 23... first bus bar;

[0098] 23a... inner bus bar portion;

[0099] 23b … outer bus bar portion;

[0100] 23c … opening portion;

[0101] 23d … connecting portion;

[0102] 24 … second bus bar;

[0103] 24a … inner bus bar portion;

[0104] 24b … outer bus bar portion;

[0105] 24c … opening portion;

[0106] 24d … connecting portion;

[0107] 25, 26 … wide portion;

[0108] 25A, 26A … quality additional film;

[0109] 27, 28 … high-speed film;

[0110] 31 … elastic wave device;

[0111] 32 … longitudinal coupling type elastic wave resonator filter;

[0112] 33 … elastic wave resonator;

[0113] P1, P2 … parallel arm resonator;

[0114] S1 to S3 … series arm resonator.

Claims

1. An elastic wave device comprising: an elastic wave resonator configured on a first piezoelectric substrate and having an IDT electrode; and a longitudinal coupling type elastic wave resonator filter configured on a second piezoelectric substrate and having a plurality of IDT electrodes, the IDT electrode of the elastic wave resonator and the IDT electrodes of the longitudinal coupling type elastic wave resonator filter each have a plurality of electrode fingers and have a crossover region in which the electrode fingers cross each other in an elastic wave propagation direction, the crossover region has a central region and first and second edge regions provided on both outer sides of the central region in a direction in which the electrode fingers extend and have a lower acoustic velocity than the central region, and first and second gap regions provided outside the direction in which the electrode fingers of the first and second edge regions extend and have a higher acoustic velocity than the central region, the lengths of the first and second edge regions in the longitudinal coupling type elastic wave resonator filter are shorter than the lengths of the first and second edge regions in the elastic wave resonator when a dimension along the direction in which the electrode fingers extend is taken as a length.

2. The elastic wave device according to claim 1, wherein the first piezoelectric substrate and the second piezoelectric substrate are the same piezoelectric substrate.

3. The elastic wave device according to claim 1, wherein the second piezoelectric substrate is a different piezoelectric substrate from the first piezoelectric substrate.

4. The elastic wave device according to any one of claims 1 to 3, wherein the widths of the electrode fingers in the first and second edge regions are greater than the widths of the electrode fingers in the central region.

5. The elastic wave device according to any one of claims 1 to 3, wherein a mass addition film is provided in the first and second edge regions so as to be laminated to the electrode fingers.

6. The elastic wave device according to claim 5, wherein the thickness of the mass addition film provided in the elastic wave resonator is the same as the thickness of the mass addition film provided in the longitudinal coupling type elastic wave resonator filter.

7. The elastic wave device according to any one of claims 1 to 3, wherein a high-velocity film is laminated to the electrode fingers in the central region.

8. The elastic wave device according to any one of claims 1 to 3, wherein the first piezoelectric substrate and the second piezoelectric substrate are a laminate in which a high-velocity material layer and a piezoelectric film are sequentially laminated, and the acoustic velocity of a bulk wave propagating in the high-velocity material layer is higher than the acoustic velocity of an elastic wave propagating in the piezoelectric film.

9. The elastic wave device according to claim 8, wherein the first piezoelectric substrate and the second piezoelectric substrate further include a low-velocity film provided between the high-velocity material layer and the piezoelectric film, and the acoustic velocity of a bulk wave propagating in the low-velocity film is lower than the acoustic velocity of a bulk wave propagating in the piezoelectric film.

10. The elastic wave device according to claim 8, wherein the high-velocity material layer is a support substrate composed of a high-velocity material. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 11. The elastic wave device of Claim 8, wherein The high acoustic velocity material layer is a high acoustic velocity film composed of a high acoustic velocity material, and further includes a support substrate that supports the high acoustic velocity material layer.

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