Elastic wave device

Abstract

Provided is an elastic wave device capable of suppressing IMD. The elastic wave device (10) of the present invention includes a piezoelectric layer (2), first and second upper electrodes (3A, 3B), first and second lower electrodes (4A, 4B), and first and second acoustic reflectors (5A, 5B). In plan view, a portion where the first upper electrode (3A) and the first lower electrode (4A) overlap is a first resonator portion (A), and a portion where the second upper electrode (3B) and the second lower electrode (4B) overlap is a second resonator portion (B). The first acoustic reflector (5A) includes a first metal layer, and the second acoustic reflector (5B) includes a second metal layer. A portion where only the first upper electrode (3A) overlaps the first metal layer in plan view is a first overlap portion (C), and a portion where only the second upper electrode (3B) overlaps the second metal layer in plan view is a second overlap portion (D). The area in plan view of the first resonator portion (A) is smaller than the area in plan view of the second resonator portion (B), and the area in plan view of the first overlap portion (C) is larger than the area in plan view of the second overlap portion (D).

Description

Technical Field

[0001] The present invention relates to an elastic wave device. Background Art

[0002] Traditionally, elastic wave devices have been widely used in filters and other applications in mobile phones. Patent Document 1 below discloses an example of an elastic wave device, a BAW (Bulk Acoustic Wave) element. In this elastic wave device, an upper electrode is provided on one principal surface of a piezoelectric layer, and a lower electrode is provided on the other principal surface of the piezoelectric layer. A reflective layer is laminated on the other principal surface of the piezoelectric layer, covering the lower electrode. The reflective layer comprises a dielectric layer made of, for example, SiO2, and a conductive layer made of, for example, tungsten. The conductive layer has an extension extending beyond the active area.

[0003] Patent Document 2 below discloses an elastic wave device that uses a series-arm resonator or a parallel-arm resonator as a ladder-type filter. This elastic wave device includes a piezoelectric layer on an acoustic reflective layer. An IDT electrode is provided on the piezoelectric layer. The acoustic reflective layer includes a dielectric layer and a metal layer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: U.S. Patent Application Publication No. 2014 / 0273881

[0007] Patent Document 2: International Publication No. 2018 / 235605 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In recent years, further improvement in filter characteristics of elastic wave devices has been sought. However, the elastic wave devices described in Patent Documents 1 and 2 may not be able to sufficiently suppress IMD (Intermodulation Distortion).

[0010] An object of the present invention is to provide an elastic wave device capable of suppressing IMD.

[0011] Means used to solve problems

[0012] In a broad aspect of an elastic wave device according to the present invention, the elastic wave device includes a first elastic wave resonator and a second elastic wave resonator electrically connected to each other, wherein the elastic wave device comprises: a piezoelectric layer having a first principal surface and a second principal surface facing each other; a first upper electrode provided on the first principal surface; a second upper electrode provided on the first principal surface; a first lower electrode provided on the second principal surface of the piezoelectric layer so as to overlap with the first upper electrode when viewed from above; and a second lower electrode provided on the second principal surface of the piezoelectric layer so as to overlap with the second upper electrode when viewed from above, wherein a portion where the first upper electrode and the first lower electrode overlap when viewed from above constitutes a first resonator portion, and a portion where the second upper electrode and the second lower electrode overlap when viewed from above constitutes a second resonator portion. The elastic wave device further comprises: a first acoustic reflection film provided on the second principal surface of the piezoelectric layer so as to overlap with the first resonator portion when viewed from above and to cover at least a portion of the first lower electrode; and a second acoustic reflection film provided The piezoelectric layer includes a first acoustic reflection membrane including at least one first metal layer, a second acoustic reflection membrane including at least one second metal layer, and a piezoelectric layer shared by the first and second elastic wave resonators. The first elastic wave resonator includes the first upper electrode, the first lower electrode, and the first acoustic reflection membrane, and the second elastic wave resonator includes the second upper electrode, the second lower electrode, and the second acoustic reflection membrane. A first overlapping portion is defined as the portion of the first upper electrode and the first lower electrode where only the first upper electrode overlaps with the first metal layer when viewed from above, and a second overlapping portion is defined as the portion of the second upper electrode and the second lower electrode where only the second upper electrode overlaps with the second metal layer when viewed from above. The first resonator has a smaller area when viewed from above than the second resonator, and the first overlapping portion has a larger area when viewed from above than the second overlapping portion.

[0013] In another broad aspect of the elastic wave device of the present invention, the elastic wave device includes a first elastic wave resonator and a second elastic wave resonator that are electrically connected to each other without intervening other elements, wherein the elastic wave device includes: a piezoelectric layer having a first principal surface and a second principal surface facing each other; a first IDT electrode provided on the first principal surface and having a plurality of electrode fingers; a second IDT electrode provided on the first principal surface and having a plurality of electrode fingers; a first wiring electrode provided on the first principal surface and connected to the first IDT electrode; and a second wiring electrode provided on the first principal surface and connected to the second IDT electrode, wherein, when viewed in the direction of elastic wave propagation, a portion of the first IDT electrode where adjacent electrode fingers overlap with each other is a first resonator portion, and a portion of the second IDT electrode where adjacent electrode fingers overlap with each other is a second resonator portion when viewed in the direction of elastic wave propagation. The elastic wave device further includes: a first acoustic reflection film provided on the The second principal surface of the piezoelectric layer is configured to overlap with the first resonator portion when viewed from above; and a second acoustic reflection membrane is provided on the second principal surface of the piezoelectric layer so as to overlap with the second resonator portion when viewed from above, the first acoustic reflection membrane including at least one first metal layer, the second acoustic reflection membrane including at least one second metal layer, the first elastic wave resonator and the second elastic wave resonator sharing the piezoelectric layer, the first elastic wave resonator including the first IDT electrode and the first acoustic reflection membrane, the second elastic wave resonator including the second IDT electrode and the second acoustic reflection membrane, the portion where the first wiring electrode and the first metal layer overlap when viewed from above being a first overlapping portion, the portion where the second wiring electrode and the second metal layer overlap being a second overlapping portion, the area of ​​the first resonator portion when viewed from above being smaller than the area of ​​the second resonator portion when viewed from above, and the area of ​​the first overlapping portion when viewed from above being larger than the area of ​​the second overlapping portion when viewed from above.

[0014] Effects of the Invention

[0015] According to the elastic wave device of the present invention, IMD can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a circuit diagram of an elastic wave device according to a first embodiment of the present invention.

[0017] Figure 2 It is a front cross-sectional view of a first elastic wave resonator and a second elastic wave resonator in the elastic wave device according to the first embodiment of the present invention.

[0018] Figure 3 FIG1 is a plan view of a first elastic wave resonator and a second elastic wave resonator in the elastic wave device according to the first embodiment of the present invention.

[0019] Figure 4 1 and 2 are diagrams illustrating IMD 3 of an elastic wave device according to the first embodiment of the present invention and a comparative example.

[0020] Figure 5 This is a circuit diagram of an elastic wave device according to a first modified example of the first embodiment of the present invention.

[0021] Figure 6 This is a circuit diagram of an elastic wave device according to a second modified example of the first embodiment of the present invention.

[0022] Figure 7 It is a plan view of an elastic wave device according to a third modified example of the first embodiment of the present invention.

[0023] Figure 8 It is a schematic front cross-sectional view of a first elastic wave resonator and a second elastic wave resonator in an elastic wave device according to a second embodiment of the present invention.

[0024] Figure 9 FIG1 is a plan view of a first elastic wave resonator and a second elastic wave resonator in an elastic wave device according to a second embodiment of the present invention. DETAILED DESCRIPTION

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

[0026] It should be noted that the various embodiments described in this specification are merely illustrative, and it is intended that some structures may be replaced or combined between different embodiments.

[0027] Figure 1 This is a circuit diagram of an elastic wave device according to a first embodiment of the present invention.

[0028] The elastic wave device 10 is a ladder-type filter. It includes multiple series-arm resonators and multiple parallel-arm resonators. In this embodiment, the elastic wave device 10 is, for example, a filter device for Wi-Fi. However, the applications of the elastic wave device 10 are not limited to the above. The passband of the elastic wave device 10 is not particularly limited.

[0029] Elastic wave device 10 includes an antenna terminal 12, a first elastic wave resonator 1A, and a second elastic wave resonator 1B. Antenna terminal 12 is connected to an antenna. In the circuit structure of elastic wave device 10, a series arm is connected to antenna terminal 12. First elastic wave resonator 1A and second elastic wave resonator 1B are each series arm resonators. First elastic wave resonator 1A and second elastic wave resonator 1B are electrically connected to each other without intervening any other components. More specifically, first elastic wave resonator 1A and second elastic wave resonator 1B are series-split resonators. In other words, first elastic wave resonator 1A and second elastic wave resonator 1B are connected in series on the path connecting antenna terminal 12 and other terminal 14, without intervening any parallel arm resonator.

[0030] It should be noted that first elastic wave resonator 1A and second elastic wave resonator 1B may be parallel arm resonators that are split in series. In this case, first elastic wave resonator 1A and second elastic wave resonator 1B are connected in series along a path connecting a node on the path connecting antenna terminal 12 and the other terminal 14 to the ground potential. However, first elastic wave resonator 1A and second elastic wave resonator 1B may also be independent resonators.

[0031] Figure 2 It is a front cross-sectional view of a first elastic wave resonator and a second elastic wave resonator in the elastic wave device according to the first embodiment.

[0032] The elastic wave device 10 includes a piezoelectric layer 2. The piezoelectric layer 2 has a first principal surface 2a and a second principal surface 2b. The first principal surface 2a and the second principal surface 2b face each other. In this specification, the first principal surface 2a is considered to be the upper side, and the second principal surface 2b is considered to be the lower side. The first elastic wave resonator 1A and the second elastic wave resonator 1B share the piezoelectric layer 2.

[0033] A first upper electrode 3A and a second upper electrode 3B are provided on the first principal surface 2a of the piezoelectric layer 2. A first lower electrode 4A and a second lower electrode 4B are provided on the second principal surface 2b. Furthermore, a first acoustic reflection membrane 5A is provided on the second principal surface 2b so as to cover the first lower electrode 4A. A second acoustic reflection membrane 5B is provided on the second principal surface 2b so as to cover the second lower electrode 4B.

[0034] The first acoustic reflection film 5A has a plurality of first low acoustic impedance layers and a plurality of first high acoustic impedance layers. It should be noted that the low acoustic impedance layer is a layer with relatively low acoustic impedance. The high acoustic impedance layer is a layer with relatively high acoustic impedance. More specifically, the acoustic impedance of the first low acoustic impedance layer is lower than the acoustic impedance of the first high acoustic impedance layer. In this embodiment, the plurality of first low acoustic impedance layers are Figure 2The first low acoustic impedance layer 6a, the first low acoustic impedance layer 6b, and the first low acoustic impedance layer 6c are shown. The multiple first high acoustic impedance layers are the first high acoustic impedance layer 7a and the first high acoustic impedance layer 7b. The multiple first low acoustic impedance layers and the multiple first high acoustic impedance layers are alternately stacked. It should be noted that at least one first low acoustic impedance layer and at least one first high acoustic impedance layer are sufficient.

[0035] The second acoustic reflection film 5B has a plurality of second low acoustic impedance layers and a plurality of second high acoustic impedance layers. The acoustic impedance of the second low acoustic impedance layer is lower than that of the second high acoustic impedance layer. In this embodiment, the plurality of second low acoustic impedance layers are Figure 2 The second low acoustic impedance layer 8a, the second low acoustic impedance layer 8b, and the second low acoustic impedance layer 8c are shown. The second high acoustic impedance layers are the second high acoustic impedance layer 9a and the second high acoustic impedance layer 9b. The second low acoustic impedance layers and the second high acoustic impedance layers are alternately stacked. It should be noted that at least one second low acoustic impedance layer and at least one second high acoustic impedance layer are sufficient.

[0036] The peripheries of the first acoustic reflection film 5A and the second acoustic reflection film 5B are covered with the intermediate layer 15. The peripheries are peripheries in a direction perpendicular to the thickness direction of the first acoustic reflection film 5A and the second acoustic reflection film 5B. Figure 2 The dashed lines in FIG represent the boundaries between the first acoustic reflection film 5A and the intermediate layer 15, and the boundaries between the second acoustic reflection film 5B and the intermediate layer 15. The intermediate layer 15 comprises an appropriate dielectric. It should be noted that the intermediate layer 15 may also comprise the same material as the first low acoustic impedance layer and the second low acoustic impedance layer.

[0037] First elastic wave resonator 1A is a resonator including first upper electrode 3A, first lower electrode 4A, and first acoustic reflection membrane 5A. Second elastic wave resonator 1B is a resonator including second upper electrode 3B, second lower electrode 4B, and second acoustic reflection membrane 5B. The overlapping portion of first upper electrode 3A and first lower electrode 4A in plan view is first resonator section A. The overlapping portion of second upper electrode 3B and second lower electrode 4B in plan view is second resonator section B. The area of ​​first resonator section A when viewed from above is smaller than the area of ​​second resonator section B when viewed from above. In this specification, "viewed from above" refers to the area from above. Figure 2 The direction of observation from above.

[0038] The first acoustic reflection film 5A may cover at least a portion of the first lower electrode 4A so as to overlap with the first resonator section A in a plan view. The second acoustic reflection film 5B may cover at least a portion of the second lower electrode 4B so as to overlap with the second resonator section B in a plan view.

[0039] The first high acoustic impedance layer 7a and the first high acoustic impedance layer 7b of the first acoustic reflective membrane 5A are first metal layers. The second high acoustic impedance layer 9a and the second high acoustic impedance layer 9b of the second acoustic reflective membrane 5B are second metal layers. It should be noted that the first acoustic reflective membrane 5A only needs to include at least one first metal layer. The second acoustic reflective membrane 5B only needs to include at least one second metal layer.

[0040] like Figure 2 As shown, a connection electrode 13 is provided on the first principal surface 2a of the piezoelectric layer 2. The connection electrode 13 electrically connects the first upper electrode 3A and the second upper electrode 3B. This electrically connects the first elastic wave resonator 1A and the second elastic wave resonator 1B. The first upper electrode 3A is configured to overlap with at least one of the first lower electrode 4A and the first acoustic reflection film 5A when viewed from above. The second upper electrode 3B is configured to overlap with at least one of the second lower electrode 4B and the second acoustic reflection film 5B when viewed from above. The connection electrode 13 is configured to not overlap with the first lower electrode 4A, the second lower electrode 4B, the first acoustic reflection film 5A, and the second acoustic reflection film 5B when viewed from above. Figure 2 The dashed-dotted line in is also a line indicating the boundary between the connection electrode 13 and the first upper electrode 3A and the second upper electrode 3B.

[0041] Figure 3 FIG1 is a top view of the first elastic wave resonator and the second elastic wave resonator in the elastic wave device according to the first embodiment. Figure 3 In FIG, hatching is used to indicate the first overlapping portion and the second overlapping portion described later. Figure 3 In FIG, wiring connecting first elastic wave resonator 1A and second elastic wave resonator 1B to other resonators and the like is omitted. Figure 3 The same applies to other top views.

[0042] like Figure 2 and Figure 3 As shown, of the first upper electrode 3A and the first lower electrode 4A, only the portion where the first upper electrode 3A overlaps with the first metal layer in a plan view is referred to as a first overlapping portion C. Of the second upper electrode 3B and the second lower electrode 4B, only the portion where the second upper electrode 3B overlaps with the second metal layer in a plan view is referred to as a second overlapping portion D. In this specification, unless otherwise specified, the areas of the first resonator section A, the second resonator section B, the first overlapping portion C, and the second overlapping portion D are the areas in a plan view.

[0043] This embodiment is characterized in that the area of ​​the first resonator section A when viewed from above is smaller than the area of ​​the second resonator section B when viewed from above, and the area of ​​the first overlapping section C when viewed from above is larger than the area of ​​the second overlapping section D when viewed from above. This can suppress IMD. The details of this effect are described together with the detailed circuit structure of this embodiment. It should be noted that, unless otherwise specified, below, "overlapping with the first upper electrode 3A when viewed from above" means overlapping with only the first upper electrode 3A, out of the first upper electrode 3A and the first lower electrode 4A. Unless otherwise specified, "overlapping with the second upper electrode 3B when viewed from above" means overlapping with only the second upper electrode 3B, out of the second upper electrode 3B and the second lower electrode 4B.

[0044] like Figure 1 As shown, elastic wave device 10 includes a plurality of resonators electrically connected to first elastic wave resonator 1A and second elastic wave resonator 1B. More specifically, first elastic wave resonator 1A, second elastic wave resonator 1B, series arm resonator S3, series arm resonator S4, and series arm resonator S5 are connected in series.

[0045] Parallel arm resonators P1 and P2 are connected between the connection point between antenna terminal 12 and first elastic wave resonator 1A and the ground potential. Parallel arm resonators P1 and P2 are connected in series. Parallel arm resonators P3 are connected between the connection point between second elastic wave resonator 1B and series arm resonator S3 and the ground potential. Parallel arm resonator P4 is connected between the connection point between series arm resonators S3 and S4 and the ground potential. Parallel arm resonators P5 and P6 are connected between series arm resonator S5 and the ground potential. Parallel arm resonators P5 and P6 are connected in series. It should be noted that the circuit structure of elastic wave device 10 is not limited to the above. For example, at least one resonator other than first elastic wave resonator 1A and second elastic wave resonator 1B may be provided. In this case, the resonator may be electrically connected to first elastic wave resonator 1A and second elastic wave resonator 1B. The resonator may be a BAW element or a SAW (Surface Acoustic Wave) element, or may be a longitudinally coupled resonator type elastic wave filter.

[0046] It should be noted that, in this embodiment, Figure 2 The piezoelectric layer 2 shown is an aluminum nitride layer. More specifically, the piezoelectric layer 2 is an AlN layer. It should be noted that the material of the piezoelectric layer 2 is not limited to the above. For example, lithium tantalate, lithium niobate, zinc oxide, quartz, or PZT (lead zirconate titanate) can also be used.

[0047] The first upper electrode 3A, the second upper electrode 3B, the first lower electrode 4A, and the second lower electrode 4B are tungsten electrodes, but the materials of the electrodes are not limited thereto.

[0048] The first and second high acoustic impedance layers are tungsten layers. Note that the materials of the first and second high acoustic impedance layers are not limited to the above, and for example, metals such as platinum and molybdenum, or dielectrics such as aluminum nitride and silicon nitride may also be used.

[0049] Each first low-acoustic impedance layer and each second low-acoustic impedance layer is a silicon oxide layer. More specifically, each of the above layers is a SiO2 layer. It should be noted that the materials of each first low-acoustic impedance layer and each second low-acoustic impedance layer are not limited to those described above; for example, metals such as aluminum can also be used. The first low-acoustic impedance layer can also be a first metal layer. Similarly, the second low-acoustic impedance layer can also be a second metal layer. However, the layer of the first acoustic reflection membrane 5A that is located closest to the piezoelectric layer 2 and covers the first lower electrode 4A is a dielectric layer. Similarly, the layer of the second acoustic reflection membrane 5B that is located closest to the piezoelectric layer 2 and covers the second lower electrode 4B is a dielectric layer.

[0050] In this embodiment, the intermediate layer 15 is made of the same material as the first and second low-acoustic-impedance layers. Specifically, the intermediate layer 15 is a SiO2 layer. However, a different material from that of the first and second low-acoustic-impedance layers may also be used for the intermediate layer 15.

[0051] Hereinafter, the effects of the present embodiment will be described by comparing the present embodiment with comparative examples.

[0052] The comparative example differs from the first embodiment in that the area of ​​the first overlapping portion C when viewed from above is smaller than the area of ​​the second overlapping portion D when viewed from above. The IMD of an elastic wave device having the structure of the first embodiment and the comparative example were compared. More specifically, the IMD3 (third-order IMD) was compared when a Band 1 transmit signal and a Band 1 receive signal were inputted through the elastic wave device's antenna terminals.

[0053] Figure 4 1 and 2 are diagrams illustrating IMDs 3 of elastic wave devices according to the first embodiment and a comparative example.

[0054] like Figure 4As shown, the first embodiment suppresses IMD3 compared to the comparative example. The reason is as follows. In both the first embodiment and the comparative example, the area of ​​the first resonator portion of the first elastic wave resonator is smaller than the area of ​​the second resonator portion of the second elastic wave resonator. In this case, the capacitance of the first elastic wave resonator is smaller than the capacitance of the second elastic wave resonator. In elastic wave resonators, smaller capacitance increases the likelihood of IMD. In the comparative example, IMD is more likely to occur in the first elastic wave resonator, and IMD in the first elastic wave resonator cannot be suppressed.

[0055] In contrast, in the first embodiment, the area of ​​the first overlapping portion C is larger than the area of ​​the second overlapping portion D. As described above, the first overlapping portion C is the portion of the first upper electrode 3A and the first lower electrode 4A where only the first upper electrode 3A overlaps with the first metal layer in a plan view. The second overlapping portion D is the portion of the second upper electrode 3B and the second lower electrode 4B where only the second upper electrode 3B overlaps with the second metal layer in a plan view. In the first elastic wave resonator 1A, the capacitance of the first overlapping portion C is added in addition to the capacitance of the first resonator section A. The capacitance of the first overlapping portion C is what is called compensation capacitance. Similarly, in the second elastic wave resonator 1B, the capacitance of the second overlapping portion D is added in addition to the capacitance of the second resonator section B. Here, because the area of ​​the first overlapping portion C is larger than that of the second overlapping portion D, the compensation capacitance added to the first elastic wave resonator 1A is larger than that added to the second elastic wave resonator 1B. This effectively suppresses IMD in the first elastic wave resonator 1A. Therefore, in the first embodiment, IMD can be suppressed in the elastic wave device 10 as a whole.

[0056] When the resonator is split in series, if the area of ​​the first resonator section A is smaller than the area of ​​the second resonator section B, as in this embodiment, the area of ​​the first overlapping section C can be made larger than the area of ​​the second overlapping section D. This can suppress IMD. As such, the present invention is particularly suitable for splitting the resonator in series.

[0057] like Figure 2As shown, the first acoustic reflection membrane 5A of the first elastic wave resonator 1A includes multiple first metal layers. When viewed from above, the entire surfaces of the multiple first metal layers overlap. However, when viewed from above, the multiple first metal layers may also have portions that do not overlap. In this case, the portion where at least one first metal layer overlaps with the first upper electrode 3A when viewed from above is the first overlapping portion C. Similarly, the portion where at least one second metal layer overlaps with the second upper electrode 3B when viewed from above is the second overlapping portion D. It should be noted that the area of ​​the portion where the first metal layer closest to the piezoelectric layer 2 overlaps with the first upper electrode 3A when viewed from above is preferably larger than the area of ​​the portion where the second metal layer closest to the piezoelectric layer 2 overlaps with the second upper electrode 3B when viewed from above. This allows for more reliable suppression of IMD.

[0058] The following describes a first and second modified examples of the first embodiment. The first and second modified examples differ from the first embodiment in circuit configuration. The first and second modified examples can also suppress IMD similarly to the first embodiment.

[0059] exist Figure 5 In the first modified example shown, first elastic wave resonator 1A and second elastic wave resonator 1B are connected in parallel with each other. More specifically, first elastic wave resonator 1A and second elastic wave resonator 1B are parallel-split resonators. In other words, first elastic wave resonator 1A and second elastic wave resonator 1B are connected in parallel with each other along the path connecting antenna terminal 12 and another terminal 14.

[0060] It should be noted that first elastic wave resonator 1A and second elastic wave resonator 1B may also be parallel arm resonators that are split in parallel. In this case, first elastic wave resonator 1A and second elastic wave resonator 1B are connected in parallel with each other on a path connecting a node on a path connecting antenna terminal 12 and another terminal 14 to ground potential. It should be noted that first elastic wave resonator 1A and second elastic wave resonator 1B may also be independent resonators. However, the present invention is particularly suitable when the resonators are split in parallel.

[0061] exist Figure 6In the second modified example shown, first elastic wave resonator 1A and second elastic wave resonator 1B are located closest to antenna terminal 12. The resonator located closest to antenna terminal 12 refers to at least one of the parallel arm resonator closest to the antenna end among the one or more parallel arm resonators and the series arm resonator closest to the antenna end among the one or more series arm resonators. Note that in this modified example, first elastic wave resonator 1A and second elastic wave resonator 1B are series-split resonators. Therefore, both first elastic wave resonator 1A and second elastic wave resonator 1B are located closest to antenna terminal 12.

[0062] When the elastic wave device is used in a multiplexer, etc., the IMD of the resonator located closest to antenna terminal 12 has a particularly significant impact on other filter devices. Therefore, when the elastic wave device of this modified example is used in a multiplexer, etc., it is possible to effectively suppress the impact of IMD on the filter device connected to both the elastic wave device and antenna terminal 12.

[0063] It should be noted that in this variation, as in the first embodiment, first elastic wave resonator 1A and second elastic wave resonator 1B are series-split resonators. In first elastic wave resonator 1A and second elastic wave resonator 1B, IMD is effectively suppressed. Therefore, first elastic wave resonator 1A or second elastic wave resonator 1B can be positioned closest to antenna terminal 12. In this case, the effects of IMD on the other filter devices described above can be effectively suppressed.

[0064] However, in the first embodiment, the first overlapping portion C is located closer to the connection electrode 13 than the first lower electrode 4A in a plan view. The second overlapping portion D is located closer to the connection electrode 13 than the second lower electrode 4B in a plan view. However, the arrangement of the first overlapping portion C and the second overlapping portion D is not limited to this. For example, Figure 7 In the third modified example of the first embodiment shown, the outer edge of the first upper electrode 23A is located around the outer edge of the first lower electrode 4A in a plan view. Consequently, the first overlapping portion C is located around the first lower electrode 4A in a plan view. Similarly, the outer edge of the second upper electrode 23B is located around the outer edge of the second lower electrode 4B in a plan view. Consequently, the second overlapping portion D is located around the second lower electrode 4B in a plan view.

[0065] In the first embodiment and its variations, the first upper electrode and the second upper electrode are connected in the first elastic wave resonator and the second elastic wave resonator. However, the first lower electrode and the second lower electrode may also be electrically connected in the first elastic wave resonator and the second elastic wave resonator.

[0066] Figure 8 It is a schematic front cross-sectional view of a first elastic wave resonator and a second elastic wave resonator in the elastic wave device according to the second embodiment. Figure 9 FIG2 is a top view of the first elastic wave resonator and the second elastic wave resonator in the elastic wave device according to the second embodiment. Figure 8 , the first elastic wave resonator and the second elastic wave resonator are shown as a simplified diagram with two diagonal lines added to a rectangle.

[0067] This embodiment is different from the first embodiment in that: Figure 8 and Figure 9 The illustrated first and second elastic wave resonators 31A and 31B are SAW elements, and the arrangement of first and second overlapping portions C and D. Except for the above-described features, the elastic wave device 30 of this embodiment has the same structure as the elastic wave device 10 of the first embodiment.

[0068] First elastic wave resonator 31A and second elastic wave resonator 31B are not electrically connected to each other via any other element. First elastic wave resonator 31A and second elastic wave resonator 31B share piezoelectric layer 2. Figure 9 As shown, a first IDT electrode 33A and a second IDT electrode 33B are provided on the first principal surface 2a of the piezoelectric layer 2. Applying an AC voltage to the first IDT electrode 33A excites elastic waves. The same applies to the second IDT electrode 33B. A pair of reflectors 34A and 34B are provided on either side of the first IDT electrode 33A on the first principal surface 2a in the direction of elastic wave propagation. A pair of reflectors 34C and 34D are provided on either side of the second IDT electrode 33B on the first principal surface 2a in the direction of elastic wave propagation.

[0069] The first IDT electrode 33A includes a first bus bar 35A, a second bus bar 36A, a plurality of first electrode fingers 37A, and a plurality of second electrode fingers 38A. One end of each of the first electrode fingers 37A is connected to the first bus bar 35A. One end of each of the second electrode fingers 38A is connected to the second bus bar 36A. The first electrode fingers 37A and the second electrode fingers 38A are alternately arranged. Similarly, the second IDT electrode 33B also includes a first bus bar 35B, a second bus bar 36B, a plurality of first electrode fingers 37B, and a plurality of second electrode fingers 38B.

[0070] As in the first embodiment, a first acoustic reflection film 5A, a second acoustic reflection film 5B, and an intermediate layer 15 are provided on the second principal surface 2b of the piezoelectric layer 2. The first elastic wave resonator 31A is a resonator including a first IDT electrode 33A, a reflector 34A, a reflector 34B, and the first acoustic reflection film 5A. The second elastic wave resonator 31B is a resonator including a second IDT electrode 33B, a reflector 34C, a reflector 34D, and the second acoustic reflection film 5B.

[0071] In the first IDT electrode 33A, the region where adjacent first and second electrode fingers 37A and 38A overlap when viewed in the direction of elastic wave propagation is the first intersection region. In this embodiment, the first intersection region represents the first resonator section A. On the other hand, in the second IDT electrode 33B, the region where adjacent first and second electrode fingers 37B and 38B overlap when viewed in the direction of elastic wave propagation is the second intersection region. The second intersection region represents the second resonator section B. The area of ​​the first resonator section A when viewed from above is smaller than the area of ​​the second resonator section B when viewed from above.

[0072] In a plan view, the first acoustic reflection membrane 5A overlaps with the first resonator part A. In a plan view, the second acoustic reflection membrane 5B overlaps with the second resonator part B.

[0073] like Figure 8 and Figure 9 As shown, first wiring electrodes 43A and 44A, as well as second wiring electrodes 43B and 44B are provided on the first principal surface 2a of the piezoelectric layer 2. The first wiring electrodes 43A and 44A are connected to the first IDT electrode 33A. More specifically, the first wiring electrode 43A is connected to the first bus bar 35A of the first IDT electrode 33A. The first wiring electrode 44A is connected to the second bus bar 36A of the first IDT electrode 33A. On the other hand, the second wiring electrodes 43B and 44B are connected to the second IDT electrode 33B. More specifically, the second wiring electrode 43B is connected to the first bus bar 35B of the second IDT electrode 33B. The second wiring electrode 44B is connected to the second bus bar 36B of the second IDT electrode 33B.

[0074] Furthermore, a connection electrode 13 is provided on the first principal surface 2a. This connection electrode 13 electrically connects the first wiring electrode 44A and the second wiring electrode 43B. This electrically connects the first elastic wave resonator 31A and the second elastic wave resonator 31B. It should be noted that the connection electrode 13 does not overlap with the first acoustic reflection film 5A and the second acoustic reflection film 5B when viewed from above. Figure 9 The dashed-dotted line in is a line indicating the boundary between the connection electrode 13 and the first wiring electrode 44A and the second wiring electrode 43B.

[0075] In this embodiment, the region where the first wiring electrode 43A and the first wiring electrode 44A overlap with the first metal layer in the first acoustic reflection membrane 5A in a plan view is the first overlapping portion C. More specifically, the region where the first wiring electrode 43A and the first wiring electrode 44A overlap with the first high acoustic impedance layer in a plan view is the first overlapping portion C. On the other hand, the region where the second wiring electrode 43B and the second wiring electrode 44B overlap with the second metal layer in the second acoustic reflection membrane 5B in a plan view is the second overlapping portion D. More specifically, the region where the second wiring electrode 43B and the second wiring electrode 44B overlap with the second high acoustic impedance layer in a plan view is the second overlapping portion D.

[0076] In the elastic wave device 30 , the area of ​​the first resonator section A in plan view is smaller than the area of ​​the second resonator section B, and the area of ​​the first overlapping portion C in plan view is larger than the area of ​​the second overlapping portion D. Therefore, IMD can be suppressed similarly to the first embodiment.

[0077] Description of Reference Numerals

[0078] 1A, 1B: a first elastic wave resonator and a second elastic wave resonator;

[0079] 2… piezoelectric layer;

[0080] 2a, 2b…first main surface, second main surface;

[0081] 3A, 3B... first upper electrode, second upper electrode;

[0082] 4A, 4B…first lower electrode, second lower electrode;

[0083] 5A, 5B…first acoustic reflection membrane, second acoustic reflection membrane;

[0084] 6a, 6b, 6c ... first low acoustic impedance layer;

[0085] 7a, 7b ... first high acoustic impedance layer;

[0086] 8a, 8b, 8c...second low acoustic impedance layer;

[0087] 9a, 9b...second high acoustic impedance layer;

[0088] 10… elastic wave device;

[0089] 12…antenna terminal;

[0090] 13…Connect the electrodes;

[0091] 14…terminal;

[0092] 15…middle layer;

[0093] 23A, 23B: a first upper electrode and a second upper electrode;

[0094] 30… elastic wave device;

[0095] 31A, 31B: a first elastic wave resonator and a second elastic wave resonator;

[0096] 33A, 33B ... a first IDT electrode and a second IDT electrode;

[0097] 34A~34D…reflector;

[0098] 35A, 35B…first bus bar;

[0099] 36A, 36B…second bus bar;

[0100] 37A, 37B...first electrode fingers;

[0101] 38A, 38B...second electrode fingers;

[0102] 43A, 44A: first wiring electrodes;

[0103] 43B, 44B ... second wiring electrodes;

[0104] A, B... first resonator section, second resonator section;

[0105] C, D…first overlapping portion, second overlapping portion;

[0106] P1~P6…parallel arm resonator;

[0107] S3~S5...series arm resonator.

Claims

1. An elastic wave device comprising a first elastic wave resonator and a second elastic wave resonator electrically connected to each other, wherein: The elastic wave device comprises: a piezoelectric layer having a first principal surface and a second principal surface facing each other; a first upper electrode disposed on the first main surface; a second upper electrode disposed on the first main surface; a first lower electrode provided on the second main surface of the piezoelectric layer so as to overlap with the first upper electrode in a plan view; as well as a second lower electrode provided on the second main surface of the piezoelectric layer so as to overlap with the second upper electrode in a plan view; The portion where the first upper electrode and the first lower electrode overlap in a plan view is a first resonator portion, and the portion where the second upper electrode and the second lower electrode overlap in a plan view is a second resonator portion. The elastic wave device further comprises: a first acoustic reflection film provided on the second main surface of the piezoelectric layer so as to overlap with the first resonator portion in a plan view and to cover at least a portion of the first lower electrode; as well as a second acoustic reflection film provided on the second main surface of the piezoelectric layer so as to overlap with the second resonator portion in a plan view and to cover at least a portion of the second lower electrode; The first acoustic reflection film includes at least one first metal layer, and the second acoustic reflection film includes at least one second metal layer. The first elastic wave resonator and the second elastic wave resonator share the piezoelectric layer, the first elastic wave resonator includes the first upper electrode, the first lower electrode, and the first acoustic reflection membrane, and the second elastic wave resonator includes the second upper electrode, the second lower electrode, and the second acoustic reflection membrane. Of the first upper electrode and the first lower electrode, only a portion of the first upper electrode overlapping with the first metal layer in a plan view is a first overlapping portion, and of the second upper electrode and the second lower electrode, only a portion of the second upper electrode overlapping with the second metal layer in a plan view is a second overlapping portion. The area of ​​the first resonator portion when viewed in plan is smaller than the area of ​​the second resonator portion when viewed in plan, and the area of ​​the first overlapping portion when viewed in plan is larger than the area of ​​the second overlapping portion when viewed in plan.

2. The elastic wave device according to claim 1, wherein The first acoustic reflective film comprises at least one first low acoustic impedance layer having relatively low acoustic impedance and at least one first high acoustic impedance layer having relatively high acoustic impedance, wherein the first low acoustic impedance layer and the first high acoustic impedance layer are alternately stacked. At least one of the first high acoustic impedance layers is the first metal layer, The second acoustic reflective film comprises at least one second low acoustic impedance layer having relatively low acoustic impedance and at least one second high acoustic impedance layer having relatively high acoustic impedance, wherein the second low acoustic impedance layer and the second high acoustic impedance layer are alternately stacked. At least one of the second high acoustic impedance layers is the second metal layer.

3. The elastic wave device according to claim 1 or 2, wherein: The first elastic wave resonator and the second elastic wave resonator are connected to each other in series.

4. The elastic wave device according to claim 1 or 2, wherein: The first elastic wave resonator and the second elastic wave resonator are connected in parallel with each other.

5. The elastic wave device according to claim 1 or 2, wherein: The elastic wave device further comprises: an antenna terminal electrically connected to the first elastic wave resonator and the second elastic wave resonator, and electrically connected to an antenna; and at least one resonator electrically connected to the first elastic wave resonator and the second elastic wave resonator, Among the first elastic wave resonator, the second elastic wave resonator, and the at least one resonator, the first elastic wave resonator or the second elastic wave resonator is arranged closest to the antenna terminal.

6. An elastic wave device comprising a first elastic wave resonator and a second elastic wave resonator electrically connected to each other without intervening any other element, wherein: The elastic wave device comprises: a piezoelectric layer having a first principal surface and a second principal surface facing each other; a first IDT electrode, which is provided on the first main surface and has a plurality of electrode fingers; a second IDT electrode, which is provided on the first main surface and has a plurality of electrode fingers; a first wiring electrode provided on the first main surface and connected to the first IDT electrode; as well as a second wiring electrode provided on the first main surface and connected to the second IDT electrode; When viewed in the direction of elastic wave propagation, the portion where the adjacent electrode fingers of the first IDT electrode overlap with each other is a first resonator portion, and when viewed in the direction of elastic wave propagation, the portion where the adjacent electrode fingers of the second IDT electrode overlap with each other is a second resonator portion. The elastic wave device further comprises: a first acoustic reflection film provided on the second main surface of the piezoelectric layer so as to overlap with the first resonator portion in a plan view; and a second acoustic reflection film provided on the second main surface of the piezoelectric layer so as to overlap with the second resonator portion in a plan view; The first acoustic reflection film includes at least one first metal layer, and the second acoustic reflection film includes at least one second metal layer. The first elastic wave resonator and the second elastic wave resonator share the piezoelectric layer. The first elastic wave resonator includes the first IDT electrode and the first acoustic reflection film. The second elastic wave resonator includes the second IDT electrode and the second acoustic reflection film. In a plan view, the portion where the first wiring electrode and the first metal layer overlap is a first overlapping portion, and the portion where the second wiring electrode and the second metal layer overlap is a second overlapping portion. The area of ​​the first resonator portion when viewed in plan is smaller than the area of ​​the second resonator portion when viewed in plan, and the area of ​​the first overlapping portion when viewed in plan is larger than the area of ​​the second overlapping portion when viewed in plan.

7. The elastic wave device according to claim 6, wherein The first acoustic reflective film comprises at least one first low acoustic impedance layer having relatively low acoustic impedance and at least one first high acoustic impedance layer having relatively high acoustic impedance, wherein the first low acoustic impedance layer and the first high acoustic impedance layer are alternately stacked. At least one of the first high acoustic impedance layers is the first metal layer, The second acoustic reflective film comprises at least one second low acoustic impedance layer having relatively low acoustic impedance and at least one second high acoustic impedance layer having relatively high acoustic impedance, wherein the second low acoustic impedance layer and the second high acoustic impedance layer are alternately stacked. At least one of the second high acoustic impedance layers is the second metal layer.

8. The elastic wave device according to claim 6 or 7, wherein: The first elastic wave resonator and the second elastic wave resonator are connected to each other in series.

9. The elastic wave device according to claim 6 or 7, wherein: The first elastic wave resonator and the second elastic wave resonator are connected in parallel with each other.

10. The elastic wave device according to claim 6 or 7, wherein: The elastic wave device further comprises: an antenna terminal electrically connected to the first elastic wave resonator and the second elastic wave resonator, and electrically connected to an antenna; and at least one resonator electrically connected to the first elastic wave resonator and the second elastic wave resonator, Among the first elastic wave resonator, the second elastic wave resonator, and the at least one resonator, the first elastic wave resonator or the second elastic wave resonator is arranged closest to the antenna terminal.

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