Elastic wave device

Abstract

Provided is an elastic wave device capable of suppressing deterioration of isolation characteristics. An elastic wave device (1) includes: a piezoelectric substrate (3); a first signal electrode (5A), a second signal electrode (6A), and a first ground electrode (7A) provided on a first main surface (3a) of the piezoelectric substrate (3); at least one insulating layer (8) provided on a second main surface (3b) of the piezoelectric substrate (3); a first signal terminal (5B) and a second signal terminal (6B) indirectly provided on the second main surface (3b) via the insulating layer (8); and a ground terminal (7B) provided on the second main surface (3b). An elastic wave filter (2) is configured from the piezoelectric substrate (3), the first signal electrode (5A) and the first signal terminal (5B) are electrically connected, the second signal electrode (6A) and the second signal terminal (6B) are electrically connected, the first ground electrode (7A) and the ground terminal (7B) are electrically connected, and the ground terminal (7B) has a contact portion (7x) in contact with the second main surface (3b) of the piezoelectric substrate (3).

Description

Technical Field

[0001] This invention relates to elastic wave devices. Background Technology

[0002] Previously, elastic wave devices have been widely used in filters for portable telephones, etc. An example of an elastic wave device is disclosed in Patent Document 1 below. In this elastic wave device, an IDT (Interdigital Transducer) electrode is provided on one main surface of a piezoelectric substrate, which is a component substrate consisting only of a piezoelectric layer. An insulating layer is provided on the other main surface of the component substrate, and multiple external electrodes are provided on the insulating layer.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 110308 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Examples of external electrodes for an elastic wave device include signal external electrodes and grounding external electrodes. When the elastic wave device is a filter device, two or more signal external electrodes are configured for both output and input. Here, the piezoelectric substrate has a high dielectric constant, resulting in a large parasitic capacitance. Therefore, in the elastic wave device described in Patent Document 1, when multiple external electrodes are signal external electrodes, coupling between the signal external electrodes via the parasitic capacitance of the piezoelectric substrate is easily generated. This can lead to a deterioration in isolation characteristics. Such deterioration in isolation characteristics becomes particularly significant when miniaturizing the elastic wave device, especially when miniaturizing or thinning the piezoelectric substrate.

[0008] The purpose of this invention is to provide an elastic wave device capable of suppressing the deterioration of isolation characteristics.

[0009] Methods for solving problems

[0010] The elastic wave device of the present invention comprises: a first piezoelectric substrate having a first main surface and a second main surface facing each other; a first functional electrode disposed on the first main surface of the first piezoelectric substrate; a first signal electrode, a second signal electrode, and a first ground electrode disposed on the first main surface of the first piezoelectric substrate; at least one insulating layer disposed on the second main surface of the first piezoelectric substrate; a first signal terminal and a second signal terminal indirectly disposed on the second main surface of the first piezoelectric substrate through the insulating layer; and a ground terminal disposed on the second main surface of the first piezoelectric substrate. A first elastic wave filter having the first functional electrode, the first signal electrode, the second signal electrode, and the first ground electrode is formed on the first piezoelectric substrate. The first signal electrode and the first signal terminal are electrically connected, the second signal electrode and the second signal terminal are electrically connected, and the first ground electrode and the ground terminal are electrically connected. The ground terminal has a contact portion that contacts the second main surface of the first piezoelectric substrate.

[0011] Invention Effects

[0012] It can provide an elastic wave device that can suppress the deterioration of isolation characteristics. Attached Figure Description

[0013] Figure 1 This is a schematic front sectional view of the elastic wave device according to the first embodiment of the present invention.

[0014] Figure 2 This is a schematic bottom view of the elastic wave device according to the first embodiment of the present invention.

[0015] Figure 3 This is a circuit diagram of the elastic wave filter according to the first embodiment of the present invention.

[0016] Figure 4 This is a schematic diagram showing the electrical connections in the comparative example.

[0017] Figure 5 This is a schematic diagram illustrating the electrical connections in the first embodiment of the present invention.

[0018] Figure 6 This is a diagram illustrating the characteristics of the isolation between the first signal terminal and the second signal terminal in the first embodiment and comparative example of the present invention.

[0019] Figure 7 This is a schematic top view of the elastic wave device according to the second embodiment of the present invention.

[0020] Figure 8 This is a schematic bottom view of the elastic wave device according to the second embodiment of the present invention.

[0021] Figure 9 This is a schematic front view of the elastic wave device according to the third embodiment of the present invention.

[0022] Figure 10 This is a schematic top view of the third and fourth elastic wave filters in the third embodiment of the present invention, viewed from above the second piezoelectric substrate.

[0023] Figure 11 This is a schematic bottom view of the elastic wave device according to the third embodiment of the present invention.

[0024] Figure 12 This is a schematic top view showing the electrode structure on the first piezoelectric substrate in the third embodiment of the present invention. Detailed Implementation

[0025] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, thereby clarifying the present invention.

[0026] In addition, it should be noted that the embodiments described in this specification are illustrative, and partial substitutions or combinations of structures can be made between different embodiments.

[0027] Figure 1 This is a schematic front sectional view of the elastic wave device according to the first embodiment of the present invention. Figure 2 This is a schematic bottom view of the elastic wave device according to the first embodiment. Additionally, Figure 1 It is along Figure 2 A sectional view along line II. Figure 1 In the diagram, a sketch is used to illustrate the IDT electrode described later by adding two diagonal lines to a rectangle. Figure 1 The same applies to the other attached figures.

[0028] like Figure 1 As shown, the elastic wave device 1 has a piezoelectric substrate 3. The piezoelectric substrate 3 is rectangular. The piezoelectric substrate 3 has a first main surface 3a and a second main surface 3b facing each other. Figure 2 As shown, the piezoelectric substrate 3 has a first side surface 3c, a second side surface 3d, a third side surface 3e, and a fourth side surface 3f. The first side surface 3c and the third side surface 3e are opposite to each other, and the second side surface 3d and the fourth side surface 3f are opposite to each other. The first side surface 3c, the second side surface 3d, the third side surface 3e, and the fourth side surface 3f are connected to the first main surface 3a and the second main surface 3b. In this specification, "top view" refers to a view taken from... Figure 1 The direction of observation from above. Looking up refers to viewing from... Figure 1The direction of observation from the lower side. In addition, the direction from the first side 3c to the third side 3e is defined as the x direction, the direction from the second side 3d to the fourth side 3f is defined as the y direction, and the direction from the second main surface 3b to the first main surface 3a is defined as the z direction.

[0029] In this embodiment, the piezoelectric substrate 3 is a lithium niobate substrate. Furthermore, the material of the piezoelectric substrate 3 is not limited to the above; for example, lithium tantalate, zinc oxide, aluminum nitride, quartz, or PZT (lead zirconate titanate) can also be used.

[0030] like Figure 1 As shown, an elastic wave filter 2 is formed on the piezoelectric substrate 3. More specifically, a plurality of IDT electrodes 4 are disposed on the first main surface 3a of the piezoelectric substrate 3. Figure 1 The diagram shows one of a plurality of IDT electrodes 4. Additionally, the elastic wave filter 2, the piezoelectric substrate 3, and the plurality of IDT electrodes 4 constitute the first elastic wave filter, the first piezoelectric substrate, and the plurality of first functional electrodes in this invention.

[0031] Furthermore, a first signal electrode 5A, a second signal electrode 6A, and a first ground electrode are provided on the first main surface 3a. The elastic wave filter 2 includes a piezoelectric substrate 3, an IDT electrode 4, a first signal electrode 5A, a second signal electrode 6A, and a first ground electrode. It is acceptable that at least one first ground electrode is provided.

[0032] Figure 3 This is a circuit diagram of the elastic wave filter in the first embodiment.

[0033] The elastic wave filter 2 includes a series arm resonator S1, a series arm resonator S2, a parallel arm resonator P1, a longitudinally coupled resonator type elastic wave filter 9A, and a longitudinally coupled resonator type elastic wave filter 9B. The series arm resonators S1 and S2 are connected between the first signal electrode 5A and the second signal electrode 6A. The longitudinally coupled resonator type elastic wave filters 9A and 9B are connected in parallel between the series arm resonators S1 and S2. The parallel arm resonator P1 is connected between the first signal electrode 5A and the ground potential. Furthermore, the IDT electrode 4 in the parallel arm resonator P1 is connected to the ground electrode, and the parallel arm resonator P1 is connected to the ground potential via the ground electrode.

[0034] Series arm resonators S1, S2, and P1 are all elastic wave resonators. More specifically, series arm resonators S1, S2, and P1 are all surface acoustic wave resonators, each having an IDT electrode 4. The longitudinally coupled resonator type elastic wave filter 9A and the longitudinally coupled resonator type elastic wave filter 9B each have multiple IDT electrodes 4. In this specification, each IDT electrode 4 is shown by the same reference numerals, but the design parameters of each IDT electrode 4 may differ depending on the desired characteristics. The same applies to the other IDT electrodes described later.

[0035] In this embodiment, the elastic wave filter 2 receives a signal from the first signal electrode 5A and outputs a signal from the second signal electrode 6A. However, the circuit structure of the elastic wave filter 2 is not limited to the above. For example, it could be a circuit structure that receives a signal from the second signal electrode 6A and outputs a signal from the first signal electrode 5A. Alternatively, the elastic wave filter 2 may simply have at least one functional electrode.

[0036] like Figure 1 as well as Figure 2 As shown, a plurality of insulating layers 8 are provided on the second main surface 3b of the piezoelectric substrate 3. In this embodiment, the insulating layer 8 is a polyimide layer. Furthermore, the material of the insulating layer is not limited to the above; for example, resins such as epoxy resins, inorganic insulators such as silicon oxide or silicon nitride, etc., can also be used. In this embodiment, the relative permittivity of the insulating layer 8 is smaller than the relative permittivity of the piezoelectric substrate 3.

[0037] A first signal terminal 5B and a second signal terminal 6B are respectively provided on each insulating layer 8. A first connecting electrode 5C is provided on the first side 3c. A second connecting electrode 6C is provided on the third side 3e. The first connecting electrode 5C is connected to the first signal terminal 5B and the first signal electrode 5A. The second connecting electrode 6C is connected to the second signal terminal 6B and the second signal electrode 6A.

[0038] Furthermore, a grounding terminal 7B is directly provided on the second main surface 3b of the piezoelectric substrate 3. Therefore, the grounding terminal 7B has a contact portion 7x that contacts the piezoelectric substrate 3. It is sufficient that at least a portion of the grounding terminal 7B contacts the second main surface 3b of the piezoelectric substrate 3. For example, a portion of the grounding terminal 7B may be indirectly provided on the second main surface 3b through an insulating layer 8. In this embodiment, multiple insulating layers 8 are provided, but at least one insulating layer 8 is sufficient. It is sufficient that the first signal terminal 5B and the second signal terminal 6B are provided on the insulating layer 8, and the grounding terminal 7B has a contact portion 7x.

[0039] In this embodiment, viewed from above, the contact portion 7x of the grounding terminal 7B is located between the first signal terminal 5B and the second signal terminal 6B. However, the contact portion 7x does not necessarily have to be located between the first signal terminal 5B and the second signal terminal 6B.

[0040] like Figure 2 As shown, a first ground connection electrode 7C is provided on the second side 3d of the piezoelectric substrate 3. The first ground connection electrode 7C is connected to the first ground electrode and the ground terminal 7B. The first ground electrode is connected to the ground potential via the first ground connection electrode 7C and the ground terminal 7B.

[0041] In the elastic wave device 1, bumps may be provided on the first signal terminal 5B, the second signal terminal 6B, and the ground terminal 7B, respectively. When the elastic wave device 1 has multiple bumps, the elastic wave device 1 is electrically connected to the outside through the multiple bumps. However, the elastic wave device 1 may also not have bumps.

[0042] In this embodiment, for the elastic wave device 1, a signal is input from the first signal terminal 5B and a signal is output from the second signal terminal 6B. Alternatively, depending on the circuit structure of the elastic wave filter 2, it can also be configured to input a signal from the second signal terminal 6B and output a signal from the first signal terminal 5B.

[0043] The feature of this embodiment is that the first signal terminal 5B and the second signal terminal 6B are indirectly disposed on the second main surface 3b of the piezoelectric substrate 3 through the insulating layer 8, and the ground terminal 7B has a contact portion 7x. This suppresses the deterioration of the isolation characteristics. This will be explained below by comparing this embodiment with a comparative example.

[0044] The comparative example differs from the first embodiment in that a grounding terminal is provided on the insulating layer, and the grounding terminal does not have a contact portion. Furthermore, in both the first embodiment and the comparative example, the relative permittivity of the insulating layer is smaller than the relative permittivity of the piezoelectric substrate.

[0045] Figure 4 This is a schematic diagram showing the electrical connections in the comparative example. Figure 5 This is a schematic diagram showing the electrical connections in the first embodiment.

[0046] like Figure 4 As shown, the insulating layer 8 and the piezoelectric substrate 3 function as capacitor elements. Therefore, it can be said that the insulating layer 8 and the piezoelectric substrate 3, acting as capacitor elements, are connected between the first signal terminal 5B and the second signal terminal 6B. Thus, the signal input from the first signal terminal 5B propagates to the second signal terminal 6B via the insulating layer 8 and the piezoelectric substrate 3. In this case, the isolation characteristics deteriorate.

[0047] Here, the ground terminal 107B is located between the first signal terminal 5B and the second signal terminal 6B. If a signal input from the first signal terminal 5B propagates towards the ground terminal 107B, its propagation to the second signal terminal 6B can be suppressed. However, an insulating layer 8 is provided between the connection point x between the first signal terminal 5B and the second signal terminal 6B and the ground terminal 107B, in addition to the piezoelectric substrate 3. Therefore, in the comparative example, a capacitor element composed of the insulating layer 8 is connected in series with a capacitor element composed of the piezoelectric substrate 3. As a result, the capacitance between the connection point x and the ground terminal 107B becomes smaller. Furthermore, as described above, the relative permittivity of the insulating layer 8 is small, thus the capacitance between the connection point x and the ground terminal 107B becomes significantly smaller. Therefore, it is difficult to ensure that the signal propagating from the first signal terminal 5B to the piezoelectric substrate 3 propagates sufficiently towards the ground terminal 107B. Therefore, it is difficult to sufficiently suppress the signal propagation from the first signal terminal 5B to the second signal terminal 6B.

[0048] In contrast, such as Figure 5 As shown, in the first embodiment, the ground terminal 7B has a contact portion 7x that contacts the piezoelectric substrate 3. No capacitor element composed of the insulating layer 8 is connected between the ground terminal 7B and the piezoelectric substrate 3. Therefore, the capacitance between the connection point x and the ground terminal 7B is greater than in the comparative example. Consequently, the signal propagating from the first signal terminal 5B to the piezoelectric substrate 3 can be sufficiently propagated towards the ground terminal 7B, and the propagation of this signal to the second signal terminal 6B can be suppressed.

[0049] Figure 6 This is a diagram illustrating the isolation characteristics between the first signal terminal and the second signal terminal in the first embodiment and the comparative example. Figure 6 The lower the ISO value on the vertical axis, the better the isolation characteristics.

[0050] like Figure 6 As shown, in the first embodiment, the ISO value becomes lower than that of the comparative example. Therefore, in the first embodiment, the degradation of the isolation characteristics can be suppressed.

[0051] like Figure 2 As shown, the contact portion 7x of the ground terminal 7B is preferably located between the first signal terminal 5B and the second signal terminal 6B when viewed from above. This allows the signal propagating from the first signal terminal 5B to the piezoelectric substrate 3 to reach the second signal terminal 6B further towards the ground terminal 7B. Therefore, the degradation of the isolation characteristics can be further suppressed.

[0052] The first signal terminal 5B and a portion of the second signal terminal 6B can also be connected to the piezoelectric substrate 3. However, it is preferable that the entire first signal terminal 5B and the second signal terminal 6B are indirectly disposed on the second main surface 3b of the piezoelectric substrate 3 through the insulating layer 8. This improves the isolation characteristics.

[0053] Figure 7 This is a schematic top view of the elastic wave device according to the second embodiment.

[0054] The elastic wave device 11 in this embodiment is a duplexer. The elastic wave device 11 includes a first elastic wave filter 12A and a second elastic wave filter 12B. The first elastic wave filter 12A has the same structure as the elastic wave filter 2 in the first embodiment. In this embodiment, the first elastic wave filter 12A and the second elastic wave filter 12B are configured on the same piezoelectric substrate 3.

[0055] More specifically, the first elastic wave filter 12A includes a piezoelectric substrate 3, a first signal electrode 5A, a second signal electrode 6A, and a plurality of first ground electrodes 7A. Furthermore, the first elastic wave filter 12A has a plurality of IDT electrodes 4 serving as a plurality of first IDT electrodes. The circuit structure of the first elastic wave filter 12A is the same as that of the elastic wave filter 2 in the first embodiment.

[0056] The second elastic wave filter 12B includes a piezoelectric substrate 3, a plurality of second IDT electrodes 14, a third signal electrode 15A, a fourth signal electrode 16A, and a second ground electrode 17A. Furthermore, as described above, the second elastic wave filter 12B shares the piezoelectric substrate 3 with the first elastic wave filter 12A. The plurality of second IDT electrodes 14, the third signal electrode 15A, the fourth signal electrode 16A, and the second ground electrode 17A are disposed on the first main surface 3a of the piezoelectric substrate 3. The second IDT electrode 14 is the second functional electrode in this invention. It is sufficient that at least one second IDT electrode 14 and one second ground electrode 17A are each provided. The circuit structure of the second elastic wave filter 12B is not particularly limited. In this embodiment, the circuit structure of the second elastic wave filter 12B is the same as that of the first elastic wave filter 12A.

[0057] In this embodiment, the first elastic wave filter 12A and the second elastic wave filter 12B share a portion of the first ground electrodes 7A. More specifically, for example, the first IDT electrode and the second IDT electrode 14 of the respective parallel arm resonators in the first elastic wave filter 12A and the second elastic wave filter 12B are connected to the same first ground electrode 7A. Alternatively, the first IDT electrode and the second IDT electrode 14 of the respective longitudinally coupled resonator type elastic wave filters in the first elastic wave filter 12A and the second elastic wave filter 12B are connected to the same first ground electrode 7A.

[0058] In this embodiment, the ground electrode shared by the first elastic wave filter 12A and the second elastic wave filter 12B is the ground electrode included by a plurality of first ground electrodes 7A. However, the ground electrode shared by the first elastic wave filter 12A and the second elastic wave filter 12B can be either the first ground electrode 7A or the second ground electrode 17A. The same applies to other embodiments where the ground electrode is shared by multiple elastic wave filters. Alternatively, the multiple elastic wave filters may not share the same ground electrode.

[0059] Figure 8 This is a schematic bottom view of the elastic wave device according to the second embodiment.

[0060] Multiple insulating layers 8 are provided on the second main surface 3b of the piezoelectric substrate 3. A first signal terminal 5B is provided on the insulating layer 8. A first connecting electrode 5C is provided on the fourth side surface 3f of the piezoelectric substrate 3. Figure 7 As shown, the first connecting electrode 5C reaches the first main surface 3a of the piezoelectric substrate 3 and the first signal electrode 5A. The first connecting electrode 5C is connected to the first signal terminal 5B and the first signal electrode 5A.

[0061] Similarly, as Figure 8 As shown, on the second main surface 3b of the piezoelectric substrate 3, a second signal terminal 6B, a third signal terminal 15B, and a fourth signal terminal 16B are respectively disposed with respect to each insulating layer 8. A third connecting electrode 15C is disposed on the fourth side surface 3f of the piezoelectric substrate 3. A second connecting electrode 6C and a fourth connecting electrode 16C are disposed on the second side surface 3d. Figure 7 as well as Figure 8 As shown, the second connecting electrode 6C is connected to the second signal terminal 6B and the second signal electrode 6A. The third connecting electrode 15C is connected to the third signal electrode 15A and the third signal terminal 15B. The fourth connecting electrode 16C is connected to the fourth signal electrode 16A and the fourth signal terminal 16B.

[0062] like Figure 8As shown, a grounding terminal 7B is directly provided on the second main surface 3b of the piezoelectric substrate 3. The grounding terminal 7B has a contact portion 7x that contacts the piezoelectric substrate 3. In the elastic wave device 11, similarly to the first embodiment, the entire grounding terminal 7B is the contact portion 7x. However, it is sufficient that at least a portion of the grounding terminal 7B contacts the second main surface 3b of the piezoelectric substrate 3.

[0063] In this embodiment, a plurality of first ground connection electrodes 7C are provided. More specifically, first ground connection electrodes 7C are respectively provided on the first side 3c, the second side 3d, and the fourth side 3f of the piezoelectric substrate 3. Furthermore, a second ground connection electrode 17C is provided on the third side 3e. The first ground connection electrode 7C, the second ground connection electrode 17C, the first connection electrode 5C, the second connection electrode 6C, the third connection electrode 15C, and the fourth connection electrode 16C are configured not to contact each other. Figure 7 as well as Figure 8 As shown, the first grounding connection electrode 7C is connected to the first grounding electrode 7A and the grounding terminal 7B. The second grounding connection electrode 17C is connected to the second grounding electrode 17A and the grounding terminal 7B.

[0064] In this embodiment, the first elastic wave filter 12A and the second elastic wave filter 12B share a single ground terminal 7B. However, the first elastic wave filter 12A and the second elastic wave filter 12B may not necessarily share a single ground terminal 7B. The elastic wave device 11 may also have a ground terminal connected to the first elastic wave filter 12A and a ground terminal connected to the second elastic wave filter 12B, respectively.

[0065] In the elastic wave device 11, signals are input from the first signal terminal 5B and the third signal terminal 15B, and signals are output from the second signal terminal 6B and the fourth signal terminal 16B. However, the directions of input and output are not limited to this.

[0066] In this embodiment, the first signal terminal 5B, the second signal terminal 6B, the third signal terminal 15B, and the fourth signal terminal 16B of each elastic wave filter are indirectly disposed on the second main surface 3b of the piezoelectric substrate 3 through the insulating layer 8. Furthermore, the ground terminal 7B has a contact portion 7x. Therefore, similar to the first embodiment, the signal propagating from the first signal terminal 5B to the piezoelectric substrate 3 can be sufficiently propagated towards the ground terminal 7B. Furthermore, the signal propagating from the third signal terminal 15B to the piezoelectric substrate 3 can also be sufficiently propagated towards the ground terminal 7B. Therefore, the propagation of the aforementioned signals to the other signal terminals can be suppressed. Consequently, the deterioration of the isolation characteristics can be suppressed.

[0067] like Figure 8As shown, preferably in top view, the contact portion 7x of the ground terminal 7B is located between the first signal terminal 5B and the third signal terminal 15B. Therefore, before the signal propagating from the first signal terminal 5B to the piezoelectric substrate 3 reaches the third signal terminal 15B, the signal can propagate further towards the ground terminal 7B. Furthermore, before the signal propagating from the third signal terminal 15B to the piezoelectric substrate 3 reaches the first signal terminal 5B, the signal can propagate further towards the ground terminal 7B. Therefore, the degradation of the isolation characteristics between the first elastic wave filter 12A and the second elastic wave filter 12B can be suppressed more effectively.

[0068] Figure 9 This is a schematic front view of the elastic wave device according to the third embodiment.

[0069] The elastic wave device 21 in this embodiment is a multiplexer. The elastic wave device 21 includes a first elastic wave filter 12A, a second elastic wave filter 12B, a third elastic wave filter 22C, and a fourth elastic wave filter 32D. The parts involving the first elastic wave filter 12A and the second elastic wave filter 12B in the elastic wave device 21 are configured in the same way as in the second embodiment.

[0070] The elastic wave device 21 includes a first piezoelectric substrate 23A and a second piezoelectric substrate 23B. The first piezoelectric substrate 23A is constructed in the same manner as the piezoelectric substrate 3 in the second embodiment. The first piezoelectric substrate 23A is indicated by the same reference numerals used for the various parts of the piezoelectric substrate 3 in the second embodiment. The second piezoelectric substrate 23B is also rectangular, similar to the first piezoelectric substrate 23A. The second piezoelectric substrate 23B has a third main surface 23a and a fourth main surface 23b facing each other.

[0071] The second piezoelectric substrate 23B has a fifth side surface 23c, a sixth side surface 23d, a seventh side surface 23e, and an eighth side surface 23f. The fifth side surface 23c, the sixth side surface 23d, the seventh side surface 23e, and the eighth side surface 23f are connected to the third main surface 23a and the fourth main surface 23b.

[0072] A first elastic wave filter 12A and a second elastic wave filter 12B are configured on a first piezoelectric substrate 23A. A third elastic wave filter 22C and a fourth elastic wave filter 32D are configured on a second piezoelectric substrate 23B. In this embodiment, the elastic wave filters configured on the first piezoelectric substrate 23A and the elastic wave filters configured on the second piezoelectric substrate 23B are arranged in a stacked manner. More specifically, the elastic wave device 21 has a plurality of bumps 28. The first piezoelectric substrate 23A and the second piezoelectric substrate 23B are joined by the plurality of bumps 28, such that the first main surface 3a of the first piezoelectric substrate 23A and the third main surface 23a of the second piezoelectric substrate 23B face each other with a gap between them.

[0073] Viewed from above, at least a portion of the first elastic wave filter 12A and the third elastic wave filter 22C overlap each other. Similarly, viewed from above, at least a portion of the second elastic wave filter 12B and the fourth elastic wave filter 32D overlap each other. This allows the elastic wave device 21 to be miniaturized. However, the positional relationship of the first elastic wave filter 12A, the second elastic wave filter 12B, the third elastic wave filter 22C, and the fourth elastic wave filter 32D in view from above is not limited to the above. Alternatively, the first elastic wave filter 12A, the second elastic wave filter 12B, the third elastic wave filter 22C, and the fourth elastic wave filter 32D may be constructed on the same piezoelectric substrate.

[0074] In this embodiment, the elastic wave device 21 has four elastic wave filters, but it is not limited to this. The elastic wave device 21, as a multiplexer, only needs to have three or more elastic wave filters.

[0075] The specific structures of the third elastic wave filter 22C and the fourth elastic wave filter 32D are described below.

[0076] Figure 10 This is a schematic top view of the second piezoelectric substrate from a perspective view of the third and fourth elastic wave filters in the third embodiment.

[0077] like Figure 10 As shown, the third elastic wave filter 22C has a second piezoelectric substrate 23B, a plurality of third IDT electrodes 24, a fifth signal electrode 25A, a sixth signal electrode 26A, and a third ground electrode 27A. The plurality of third IDT electrodes 24, the fifth signal electrode 25A, the sixth signal electrode 26A, and the third ground electrode 27A are disposed on the third main surface 23a of the second piezoelectric substrate 23B. The third IDT electrode 24 is the third functional electrode in this invention. It is sufficient that at least one of each of the third IDT electrode 24 and the third ground electrode 27A is provided.

[0078] The fourth elastic wave filter 32D has a second piezoelectric substrate 23B, a plurality of fourth IDT electrodes 34, a seventh signal electrode 35A, an eighth signal electrode 36A, and a fourth ground electrode 37A. The plurality of fourth IDT electrodes 34, the seventh signal electrode 35A, the eighth signal electrode 36A, and the fourth ground electrode 37A are disposed on the third main surface 23a of the second piezoelectric substrate 23B. Furthermore, at least one fourth IDT electrode 34 is required. The third elastic wave filter 22C and the fourth elastic wave filter 32D share the second piezoelectric substrate 23B. Furthermore, the third elastic wave filter 22C and the fourth elastic wave filter 32D share the third ground electrode 27A and the fourth ground electrode 37A.

[0079] In this embodiment, the circuit structures of the third elastic wave filter 22C and the fourth elastic wave filter 32D are the same as those of the first elastic wave filter 12A. However, the circuit structures of the third elastic wave filter 22C and the fourth elastic wave filter 32D are not limited to those described above.

[0080] like Figure 10 As shown, protrusions 28 are respectively provided on the 5th signal electrode 25A, the 6th signal electrode 26A, the 7th signal electrode 35A, the 8th signal electrode 36A, the 3rd ground electrode 27A, and the 4th ground electrode 37A. Figure 9 As shown, these bumps 28 connect the first piezoelectric substrate 23A and the second piezoelectric substrate 23B.

[0081] In this embodiment, the signal terminals for connecting the third elastic wave filter 22C and the fourth elastic wave filter 32D to the outside are provided on the second main surface 3b of the first piezoelectric substrate 23A. The connection method of each signal terminal and the aforementioned signal electrodes will be specifically described below.

[0082] Figure 11 This is a schematic bottom view of the elastic wave device according to the third embodiment. Figure 12 This is a schematic top view showing the electrode structure on the first piezoelectric substrate in the third embodiment.

[0083] like Figure 11 As shown, in this embodiment, a plurality of insulating layers 8 are provided near each corner of the second main surface 3b of the first piezoelectric substrate 23A. A fifth signal terminal 25B, a sixth signal terminal 26B, a seventh signal terminal 35B, and an eighth signal terminal 36B are respectively provided on each insulating layer 8. Furthermore, similar to the second embodiment, a first signal terminal 5B, a second signal terminal 6B, a third signal terminal 15B, and a fourth signal terminal 16B are provided on the second main surface 3b, separated by the other insulating layers 8. However, the positional relationship of the signal terminals is not limited to the above description.

[0084] A fifth connecting electrode 25C and a sixth connecting electrode 26C are disposed on a first side surface 3c of the first piezoelectric substrate 23A. A seventh connecting electrode 35C and an eighth connecting electrode 36C are disposed on a third side surface 3e. Furthermore, in this embodiment, a first ground connecting electrode 7C is located between the fifth connecting electrode 25C and the sixth connecting electrode 26C. A second ground connecting electrode 17C is located between the seventh connecting electrode 35C and the eighth connecting electrode 36C.

[0085] On the other hand, such as Figure 12As shown, in this embodiment, a first pad electrode 25D, a second pad electrode 26D, a third pad electrode 35D, and a fourth pad electrode 36D are provided near each corner of the first main surface 3a of the first piezoelectric substrate 23A. The fifth connecting electrode 25C is connected to the first pad electrode 25D and the fifth signal terminal 25B. The sixth connecting electrode 26C is connected to the second pad electrode 26D and the sixth signal terminal 26B. The seventh connecting electrode 35C is connected to the third pad electrode 35D and the seventh signal terminal 35B. The eighth connecting electrode 36C is connected to the fourth pad electrode 36D and the eighth signal terminal 36B.

[0086] like Figure 9 As shown, the second pad electrode 26D and the sixth signal electrode 26A are joined by bumps 28. The fourth pad electrode 36D and the eighth signal electrode 36A are joined by bumps 28. Similarly, the first pad electrode 25D and the fifth signal electrode 25A are joined by bumps 28, and the third pad electrode 35D and the seventh signal electrode 35A are joined by bumps 28. Furthermore, the third ground electrode 27A and the fourth ground electrode 37A are also joined to the first ground electrode 7A by bumps 28, respectively. Thus, the first piezoelectric substrate 23A and the second piezoelectric substrate 23B are joined.

[0087] As described above, the fifth signal electrode 25A is electrically connected to the fifth signal terminal 25B via bump 28, the first pad electrode 25D, and the fifth connection electrode 25C. The sixth signal electrode 26A is electrically connected to the sixth signal terminal 26B via bump 28, the second pad electrode 26D, and the sixth connection electrode 26C. The seventh signal electrode 35A is electrically connected to the seventh signal terminal 35B via bump 28, the third pad electrode 35D, and the seventh connection electrode 35C. The eighth signal electrode 36A is electrically connected to the eighth signal terminal 36B via bump 28, the fourth pad electrode 36D, and the eighth connection electrode 36C. Furthermore, the third ground electrode 27A and the fourth ground electrode 37A are electrically connected to the ground terminal 7B via bump 28, the first ground electrode 7A, and the first ground connection electrode 7C, respectively.

[0088] In this embodiment, all elastic wave filters share a common ground terminal 7B. However, the first elastic wave filter 12A, the second elastic wave filter 12B, the third elastic wave filter 22C, and the fourth elastic wave filter 32D may not necessarily share a common ground terminal 7B.

[0089] like Figure 9As shown, bumps 38 are provided on the second signal terminal 6B, the fourth signal terminal 16B, the sixth signal terminal 26B, the eighth signal terminal 36B, and the ground terminal 7B, respectively. Similarly, bumps 38 are also provided on the first signal terminal 5B, the third signal terminal 15B, the fifth signal terminal 25B, and the seventh signal terminal 35B, respectively. The elastic wave device 21 is mounted on an external mounting plate or the like via the aforementioned bumps 38 and is electrically connected to the outside.

[0090] In the elastic wave device 21, signals are input from the first signal terminal 5B, the third signal terminal 15B, the fifth signal terminal 25B, and the seventh signal terminal 35B. On the other hand, signals are output from the second signal terminal 6B, the fourth signal terminal 16B, the sixth signal terminal 26B, and the eighth signal terminal 36B. However, the directions of input and output are not limited to these.

[0091] like Figure 11 As shown, in this embodiment, the first signal terminal 5B, the second signal terminal 6B, the third signal terminal 15B, and the fourth signal terminal 16B of each elastic wave filter are indirectly disposed on the second main surface 3b of the first piezoelectric substrate 23A through the insulating layer 8. Furthermore, the fifth signal terminal 25B, the sixth signal terminal 26B, the seventh signal terminal 35B, and the eighth signal terminal 36B of the other elastic wave filters are indirectly disposed on the second main surface 3b of the first piezoelectric substrate 23A through the insulating layer 8. Moreover, the ground terminal 7B has a contact portion 7x. Therefore, similar to the second embodiment, signals propagating from the first signal terminal 5B to the first piezoelectric substrate 23A and signals propagating from the third signal terminal 15B to the first piezoelectric substrate 23A can be sufficiently propagated towards the ground terminal 7B. Furthermore, signals propagating from the 5th signal terminal 25B to the 1st piezoelectric substrate 23A and signals propagating from the 7th signal terminal 35B to the 1st piezoelectric substrate 23A can also be sufficiently propagated towards the ground terminal 7B. Therefore, the propagation of the aforementioned signals to the other signal terminals can be suppressed. Consequently, the deterioration of the isolation characteristics can be suppressed.

[0092] Viewed from above, the contact portion 7x of the preferred ground terminal 7B is located between the first signal terminal 5B and the fifth signal terminal 25B. This allows the signal propagating from the first signal terminal 5B to the first piezoelectric substrate 23A to reach the fifth signal terminal 25B, allowing the signal to propagate further towards the ground terminal 7B. Furthermore, it allows the signal propagating from the fifth signal terminal 25B to the first piezoelectric substrate 23A to reach the first signal terminal 5B, allowing the signal to propagate further towards the ground terminal 7B. Therefore, the degradation of the isolation characteristics between the first elastic wave filter 12A and the third elastic wave filter 22C can be suppressed more effectively.

[0093] Similarly, the contact portion 7x of the grounding terminal 7B is preferably located between the first signal terminal 5B and the third signal terminal 15B, and between the first signal terminal 5B and the seventh signal terminal 35B. This allows for more effective suppression of the degradation of the isolation characteristics between the first elastic wave filter 12A and the second elastic wave filter 12B, and between the first elastic wave filter 12A and the fourth elastic wave filter 32D.

[0094] Furthermore, signal electrodes for the first elastic wave filter 12A and the second elastic wave filter 12B are provided on the first main surface 3a of the first piezoelectric substrate 23A. On the other hand, in addition to the signal terminals of the first elastic wave filter 12A and the second elastic wave filter 12B, signal terminals for the third elastic wave filter 22C and the fourth elastic wave filter 32D are also provided on the second main surface 3b. Therefore, the elastic wave filters configured on the first piezoelectric substrate 23A and the second piezoelectric substrate 23B can be suitably arranged in a stacked configuration. Thus, the elastic wave device 21 can be made smaller.

[0095] As described above, the number of signal terminals provided on the second main surface 3b is greater than the number of signal electrodes provided on the first main surface 3a, thus making it easier to reduce the area of ​​the ground terminal 7B. In this embodiment, the ground terminal 7B has a contact portion 7x that contacts the first piezoelectric substrate 23A. Therefore, even with a smaller area of ​​the ground terminal 7B, the propagation of input signals to other signal terminals can be effectively suppressed. Consequently, the elastic wave device 21 can be made smaller, and the deterioration of isolation characteristics can be suppressed.

[0096] Explanation of reference numerals in the attached figures

[0097] 1…elastic wave device;

[0098] 2… Elastic wave filter;

[0099] 3…Piezoelectric substrate;

[0100] 3a, 3b... First and second main faces;

[0101] 3c~3f… Side views 1 to 4;

[0102] 4…IDT electrodes;

[0103] 5A…First signal electrode;

[0104] 5B…Signal Terminal 1;

[0105] 5C…First connecting electrode;

[0106] 6A…Second signal electrode;

[0107] 6B…Second signal terminal;

[0108] 6C…Second connecting electrode;

[0109] 7A…First grounding electrode;

[0110] 7B…Grounding terminal;

[0111] 7C…First ground connection electrode;

[0112] 7x…contact parts;

[0113] 8…Insulation layer;

[0114] 9A, 9B... longitudinally coupled resonator type elastic wave filter;

[0115] 11…elastic wave device;

[0116] 12A, 12B… First and second elastic wave filters;

[0117] 14…Second IDT electrode;

[0118] 15A…Third signal electrode;

[0119] 15B…3rd signal terminal;

[0120] 15C…Third connecting electrode;

[0121] 16A…4th signal electrode;

[0122] 16B…4th signal terminal;

[0123] 16C…4th connecting electrode;

[0124] 17A…Second grounding electrode;

[0125] 17C…Second ground connection electrode;

[0126] 21…elastic wave device;

[0127] 22C…3rd elastic wave filter;

[0128] 23A, 23B… First and second piezoelectric substrates;

[0129] 23a, 23b… the 3rd and 4th main faces;

[0130] 23c~23f…5th~8th side views;

[0131] 24…3rd IDT electrode;

[0132] 25A…5th signal electrode;

[0133] 25B…5th signal terminal;

[0134] 25C…5th connecting electrode;

[0135] 25D…First pad electrode;

[0136] 26A…Sixth signal electrode;

[0137] 26B…Signal terminal number 6;

[0138] 26C…6th connecting electrode;

[0139] 26D…Second pad electrode;

[0140] 27A…Third grounding electrode;

[0141] 28…bumps;

[0142] 32D…4th elastic wave filter;

[0143] 34…4th IDT electrode;

[0144] 35A…7th signal electrode;

[0145] 35B…Signal terminal number 7;

[0146] 35C…7th connecting electrode;

[0147] 35D…3rd pad electrode;

[0148] 36A…8th signal electrode;

[0149] 36B…8th signal terminal;

[0150] 36C…8th connecting electrode;

[0151] 36D…4th pad electrode;

[0152] 37A…4th grounding electrode;

[0153] 38…bumps;

[0154] 107B…Grounding terminal;

[0155] P1…parallel arm resonator;

[0156] S1, S2... series arm resonators;

[0157] x...connection point.

Claims

1. An elastic wave device, comprising: The first piezoelectric substrate has a first main surface and a second main surface that are opposite to each other; The first functional electrode is disposed on the first main surface of the first piezoelectric substrate; The first signal electrode, the second signal electrode, and the first ground electrode are disposed on the first main surface of the first piezoelectric substrate; At least one insulating layer is disposed on the second main surface of the first piezoelectric substrate; The first signal terminal and the second signal terminal are indirectly disposed on the second main surface of the first piezoelectric substrate through the insulating layer; and A grounding terminal is disposed on the second main surface of the first piezoelectric substrate. A first elastic wave filter having the first functional electrode, the first signal electrode, the second signal electrode, and the first ground electrode is formed on the first piezoelectric substrate. The first signal electrode and the first signal terminal are electrically connected, the second signal electrode and the second signal terminal are electrically connected, and the first ground electrode and the ground terminal are electrically connected. The grounding terminal has a contact portion that contacts the second main surface of the first piezoelectric substrate.

2. The elastic wave device according to claim 1, wherein, Viewed from above, the contact portion of the grounding terminal is located between the first signal terminal and the second signal terminal.

3. The elastic wave device according to claim 1 or 2, wherein, It also has: The second functional electrode is disposed on the first main surface of the first piezoelectric substrate; The third signal electrode, the fourth signal electrode, and the second ground electrode are disposed on the first main surface of the first piezoelectric substrate; and The third signal terminal and the fourth signal terminal are indirectly disposed on the second main surface of the first piezoelectric substrate through the insulating layer. A second elastic wave filter, comprising the second functional electrode, the third signal electrode, the fourth signal electrode, and the second ground electrode, is formed on the first piezoelectric substrate. In the first piezoelectric substrate, the third signal electrode and the third signal terminal are electrically connected, the fourth signal electrode and the fourth signal terminal are electrically connected, and the second ground electrode and the ground terminal are electrically connected. Viewed from above, the contact portion of the grounding terminal is located between the first signal terminal and the third signal terminal.

4. The elastic wave device according to claim 3, wherein, Signals are input from the first signal terminal and the third signal terminal, and signals are output from the second signal terminal and the fourth signal terminal.

5. The elastic wave device according to claim 1 or 2, wherein, It also has: The second piezoelectric substrate has a third main surface and a fourth main surface that are opposite to each other; The third functional electrode is disposed on the third main surface of the second piezoelectric substrate; The fifth signal electrode, the sixth signal electrode, and the third ground electrode are disposed on the third main surface of the second piezoelectric substrate; and The fifth and sixth signal terminals are indirectly disposed on the second main surface of the first piezoelectric substrate through the insulating layer. The second piezoelectric substrate forms a third elastic wave filter having the third functional electrode, the fifth signal electrode, the sixth signal electrode, and the third ground electrode. The fifth signal electrode and the fifth signal terminal are electrically connected, the sixth signal electrode and the sixth signal terminal are electrically connected, and the third ground electrode and the ground terminal are electrically connected. Viewed from above, the contact portion of the grounding terminal is located between the first signal terminal and the fifth signal terminal.

6. The elastic wave device according to claim 5, wherein, Signals are input from the first signal terminal and the fifth signal terminal, and signals are output from the second signal terminal and the sixth signal terminal.

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