JPWO2011142183A1 - Surface acoustic wave device - Google Patents

Abstract

A surface acoustic wave device in which spurious and ripples are suppressed and has excellent resonance characteristics and filter characteristics is provided. The surface acoustic wave device 1 includes a piezoelectric substrate 10, an IDT electrode 11, and a dielectric layer 16. The region where the IDT electrode 11 is formed includes a crossing region C and a non-crossing region D. In the intersecting region C, the electrode finger 12a of the first comb-shaped electrode 12 and the electrode finger 13a of the second comb-shaped electrode 13 adjacent to the electrode finger 12a intersect in the intersecting width direction y. It is an area. In the non-intersecting region D, the electrode finger 12a of the first comb-shaped electrode 12 and the electrode finger 13a of the second comb-shaped electrode 13 adjacent to the electrode finger 12a intersect in the intersecting width direction y. It is an area that is not. This is a portion formed in the non-intersecting region C of the dielectric layer 16. The non-intersecting region portion 16a includes portions having different thicknesses in the intersecting width direction y.

Description

  The present invention relates to a surface acoustic wave device, and more particularly, to a surface acoustic wave device including an IDT electrode formed on a piezoelectric substrate and a dielectric layer formed so as to cover the IDT electrode.

  Conventionally, a surface acoustic wave device is mounted as a duplexer, an interstage filter, or the like on an RF (Radio Frequency) circuit in a communication device such as a mobile phone.

The surface acoustic wave device has an IDT electrode formed on a piezoelectric substrate, and a surface acoustic wave excited by the IDT electrode propagates on the surface of the piezoelectric substrate. In the surface acoustic wave device, a LiTaO ₃ substrate, a LiNbO ₃ substrate, or the like is used as the piezoelectric substrate. These piezoelectric substrates have a negative frequency temperature coefficient (TCF: Temperature Coefficient of Frequency). Specifically, the TCF of the LiNbO ₃ substrate is about −90 to −70 ppm / ° C., and the TCF of the LiTaO ₃ substrate is about −40 to −30 ppm / ° C. For this reason, surface acoustic wave devices in which only IDT electrodes are formed on these piezoelectric substrates have a problem that it is difficult to obtain excellent frequency temperature characteristics required for duplexers and interstage filters.

In view of such a problem, for example, in Patent Document 1 below, it is formed on a piezoelectric substrate such as a LiTaO ₃ substrate or a LiNbO ₃ substrate, and is made of a high-density metal such as Au, Ag, Cu, or Pt. It has been proposed to form a dielectric layer made of SiO ₂ having a positive TCF so as to cover the IDT electrode, and to flatten the surface of the dielectric layer. Patent Document 1 describes that by adopting such a configuration, an excellent frequency temperature characteristic and a large reflection coefficient can be realized.

JP 2006-254507 A

  However, the surface acoustic wave device described in Patent Document 1 has a problem in that spurious and ripples occur, and the resonator characteristics and filter characteristics may deteriorate.

  An object of the present invention is to solve such a problem and to provide a surface acoustic wave device in which spurious and ripples are suppressed and which has excellent resonance characteristics and filter characteristics.

  A surface acoustic wave device according to the present invention includes a piezoelectric substrate, an IDT electrode, and a dielectric layer. The IDT electrode is formed on the piezoelectric substrate. The dielectric layer is formed on the piezoelectric substrate so as to cover the IDT electrode. The IDT electrode includes first and second comb-like electrodes. Each of the first and second comb-like electrodes has a plurality of electrode fingers. The first and second comb-like electrodes are interleaved with each other. The region where the IDT electrode is formed includes a crossing region and a non-crossing region. The intersecting region is an intersecting width direction in which the electrode finger of the first comb-shaped electrode and the electrode finger of the second comb-shaped electrode adjacent to the electrode finger are perpendicular to the surface acoustic wave propagation direction. It is the area | region which cross | intersects. The non-intersecting region is a region where the electrode finger of the first comb-shaped electrode and the electrode finger of the second comb-shaped electrode adjacent to the electrode finger do not intersect in the intersecting width direction. The non-crossing region portion, which is a portion formed in the non-crossing region of the dielectric layer, includes a portion having a different thickness in the crossing width direction.

  In a specific aspect of the surface acoustic wave device according to the present invention, the IDT electrodes are weighted with cross width. The first comb-like electrode has a dummy electrode finger facing the tip of the electrode finger of the second comb-like electrode in the cross width direction. The second comb-like electrode has a dummy electrode finger facing the tip portion of the electrode finger of the first comb-like electrode in the cross width direction. The dummy electrode fingers of the first and second comb-like electrodes are arranged in the non-intersecting region.

  In another specific aspect of the surface acoustic wave device according to the present invention, the thickness of the non-intersecting region portion gradually changes in the intersecting width direction. According to this configuration, spurious and ripple can be more effectively suppressed.

  In another specific aspect of the surface acoustic wave device according to the present invention, the surface of the non-intersecting region portion has a portion extending in a direction inclined with respect to the surface of the piezoelectric substrate in the intersecting width direction.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the non-intersecting region portion includes a first portion and a second portion adjacent to the first portion in the intersecting width direction. A step is formed between the surface of the first part and the surface of the second part.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the surface of the intersecting region portion, which is a portion formed in the intersecting region of the dielectric layer, is parallel and flat to the surface of the piezoelectric substrate. According to this configuration, more excellent frequency temperature characteristics can be realized.

  In still another specific aspect of the surface acoustic wave device according to the present invention, each of the first and second comb electrodes has a bus bar to which a plurality of electrode fingers are connected. The plurality of electrode fingers are constituted by the first conductive film. The bus bar is composed of a first conductive film and a second conductive film formed on the first conductive film.

  In still another specific aspect of the surface acoustic wave device according to the present invention, the surface acoustic wave device further includes a pair of reflectors located on both sides of the surface acoustic wave propagation direction in the region where the IDT electrode is provided. The reflector is covered with a dielectric layer. The part of the region where the reflector of the dielectric layer is formed includes a part having a different thickness in the intersecting width direction.

  Another surface acoustic wave device according to the present invention includes a piezoelectric substrate, an IDT electrode, a pair of reflectors, and a dielectric layer. The IDT electrode is formed on the piezoelectric substrate. The reflectors are located on both sides of the surface acoustic wave propagation direction in the region where the IDT electrode is provided. The dielectric layer is formed on the piezoelectric substrate so as to cover the IDT electrode and the reflector. The IDT electrode includes first and second comb-like electrodes. Each of the first and second comb-like electrodes has a plurality of electrode fingers. The first and second comb-like electrodes are interleaved with each other. The region where the IDT electrode is formed includes a crossing region. The intersecting region is an intersecting width direction in which the electrode finger of the first comb-shaped electrode and the electrode finger of the second comb-shaped electrode adjacent to the electrode finger are perpendicular to the surface acoustic wave propagation direction. It is the area | region which cross | intersects. The part of the region where the reflector of the dielectric layer is formed includes a part having a different thickness in the intersecting width direction.

  In a specific aspect of the surface acoustic wave device according to the present invention and another surface acoustic wave device according to the present invention, the dielectric layer is formed by a bias sputtering method. For this reason, it is difficult to form a gap between the dielectric layer and the IDT electrode, and the reliability of the surface acoustic wave device can be improved.

  In the present invention, the reflection of the surface acoustic wave of the dielectric layer, such as the non-crossing region portion, the portion of the dielectric layer where the reflector is formed, such as the portion formed in the non-crossing region of the dielectric layer. The portion formed in the region includes a portion having a different thickness in the intersecting width direction. Therefore, spurious and ripple can be suppressed, and excellent resonance characteristics and filter characteristics can be obtained.

FIG. 1 is a schematic plan view of a surface acoustic wave device according to a first embodiment of the present invention. In FIG. 1, drawing of the dielectric layer and the protective layer is omitted. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. FIG. 4 is a schematic cross-sectional view of a surface acoustic wave device according to a comparative example. FIG. 5 is a graph showing impedance characteristics of the surface acoustic wave device according to the example and the surface acoustic wave device according to the comparative example. In FIG. 5, the solid line represents the impedance characteristic of the surface acoustic wave device according to the example. A dashed line represents the impedance characteristic of the surface acoustic wave device according to the comparative example. FIG. 6 is a graph showing return losses of the surface acoustic wave device according to the example and the surface acoustic wave device according to the comparative example. In FIG. 6, the solid line represents the return loss of the surface acoustic wave device according to the example. A dashed line represents a return loss of the surface acoustic wave device according to the comparative example. FIG. 7 shows a surface acoustic wave device according to an example in which the film thickness difference wavelength ratio of the dielectric layer is 1.2%, 2.0%, 3.2%, and 5.1%, and the dielectric It is a graph showing each impedance characteristic of the surface acoustic wave apparatus which concerns on the comparative example whose film thickness difference wavelength ratio of a layer is 0%. FIG. 8 shows a surface acoustic wave device according to an example in which the film thickness difference wavelength ratio of the dielectric layer is 1.2%, 2.0%, 3.2%, and 5.1%, and the dielectric It is a graph showing each return loss of the surface acoustic wave apparatus which concerns on the comparative example whose film thickness difference wavelength ratio of a layer is 0%. FIG. 9 is a schematic cross-sectional view of a surface acoustic wave device according to a first modification of the present invention. FIG. 10 is a schematic plan view of a surface acoustic wave device according to a second modification of the present invention. In FIG. 10, drawing of the dielectric layer and the protective layer is omitted. FIG. 11 is a schematic plan view of a surface acoustic wave device according to a third modification of the present invention. In FIG. 11, drawing of the dielectric layer and the protective layer is omitted. FIG. 12 is a schematic circuit diagram of a surface acoustic wave device according to a second embodiment of the present invention. FIG. 13 is a schematic plan view of a surface acoustic wave device according to a third embodiment of the present invention. In FIG. 13, drawing of the dielectric layer and the protective layer is omitted. FIG. 14 is a schematic circuit diagram of a surface acoustic wave device according to a fourth embodiment of the present invention.

(First embodiment)
FIG. 1 is a schematic plan view of a surface acoustic wave device 1 according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line II-II in FIG. 3 is a schematic cross-sectional view taken along line III-III in FIG. In FIG. 1, drawing of the dielectric layer 16 and the protective layer 17 is omitted.

  Hereinafter, a preferred embodiment of the present invention will be described taking the surface acoustic wave device 1 shown in FIG. 1 as an example. A surface acoustic wave device 1 shown in FIG. 1 is a one-port surface acoustic wave resonator that uses a Rayleigh wave (P + SV wave) as a main mode. However, the surface acoustic wave device 1 is merely an example. The surface acoustic wave device according to the present invention is not limited to the surface acoustic wave device 1. The surface acoustic wave device according to the present invention may be a surface acoustic wave filter, a surface acoustic wave duplexer, or the like. The surface acoustic wave device according to the present invention may use a surface acoustic wave other than a Rayleigh wave such as a Love wave as the main mode.

As shown in FIGS. 1 to 3, the surface acoustic wave device 1 includes a piezoelectric substrate 10. The piezoelectric substrate 10 can be formed of an appropriate piezoelectric body. The piezoelectric substrate 10 can be composed of, for example, a piezoelectric single crystal substrate such as a LiNbO ₃ substrate, a LiTaO ₃ substrate, or a quartz substrate. Specifically, in the present embodiment, the piezoelectric substrate 10 is composed of a 127 ° Y-cut X-propagation LiNbO ₃ substrate.

  As shown in FIG. 1, on the piezoelectric substrate 10, there are an IDT electrode 11 and a pair of reflectors 14 and 15 located on both sides of the surface acoustic wave propagation direction x in a region where the IDT electrode 11 is provided. Is formed.

  The IDT electrode 11 includes first and second comb-like electrodes 12 and 13. Each of the first and second comb-like electrodes 12 and 13 is connected to a plurality of electrode fingers 12a and 13a arranged along the surface acoustic wave propagation direction x and a plurality of electrode fingers 12a and 13a. Bus bars 12c and 13c. The first and second comb-shaped electrodes 12 and 13 are interleaved with each other. In other words, the first and second comb electrodes 12 and 13 are provided such that the electrode fingers 12a and 13a are alternately arranged in the surface acoustic wave propagation direction x. The first comb-like electrode 12 has a dummy electrode finger 12b facing the tip of each electrode finger 13a of the second comb-like electrode 13 in the cross width direction y. The intersecting width direction y is perpendicular to the surface acoustic wave propagation direction x. The dummy electrode fingers 12b are also connected to the bus bar 12c. Similarly, the second comb-like electrode 13 also has a dummy electrode finger 13b facing the tip of each electrode finger 12a of the first comb-like electrode 12 in the cross width direction y. The dummy electrode fingers 13b are also connected to the bus bar 13c.

  In the present embodiment, the IDT electrode 11 is subjected to cross width weighting. That is, the IDT electrode 11 is configured such that the intersection width, which is the width at which the adjacent electrode fingers 12a and 13a intersect in the intersection width direction y, changes in the surface acoustic wave propagation direction x. Specifically, in the present embodiment, the IDT electrode 11 is weighted in the cross width so that a plurality of maximum values of the cross width appear in the surface acoustic wave propagation direction x. For this reason, in this embodiment, the Q value at the antiresonance frequency of the surface acoustic wave device 1 is increased, and the power durability of the surface acoustic wave device 1 is increased.

  Here, a virtual line formed by connecting the tips of the electrode fingers 12a in the cross width direction y is defined as a first envelope A. A virtual line formed by connecting the tips of the electrode fingers 13a in the cross width direction y is defined as a second envelope B. Each of the first and second envelopes A and B includes a first envelope portion A1, A3, B1, and B3 inclined to one side in the surface acoustic wave propagation direction x, and a surface acoustic wave propagation direction x. , The second envelope portions A2, A4, B2, and B4 inclined to the other side are provided. In each of the first and second envelopes A and B, the first envelope portions A1, A3, B1 and B3 and the second envelope portions A2, A4, B2 and B4 are propagated by surface acoustic wave propagation. They are arranged alternately in the direction x.

  Of the region where the IDT electrode 11 is provided, the region surrounded by the first and second envelopes A and B is the intersection region C, and the first and second envelopes A in the intersection width direction y. , B is a non-intersecting region D. In the intersecting region C, the electrode finger 12a of the first comb-shaped electrode 12 and the electrode finger 13a of the second comb-shaped electrode 13 adjacent to the electrode finger 12a intersect each other. By applying a voltage to the electrode fingers 12a and 13a, a surface acoustic wave is excited in the intersection region C. That is, the intersection region C is a surface acoustic wave excitation region.

  On the other hand, in the non-intersecting region D, dummy electrode fingers 12b and 13b are located on both sides of the surface acoustic wave propagation direction x of the electrode fingers 12a and 13a. In the non-intersecting region D, the electrode finger 12a of the first comb-shaped electrode 12 and the electrode finger 13a of the second comb-shaped electrode 13 adjacent to the electrode finger 12a do not intersect. In the non-intersecting region D, the surface acoustic waves are not excited, and the surface acoustic waves excited in the intersecting region C are reflected by the dummy electrode fingers 12b and 13b. That is, the non-intersecting region D is a surface acoustic wave reflection region.

  The reflectors 14 and 15 are grating reflectors. The surface acoustic wave excited in the intersecting region C of the IDT electrode 11 is reflected by the reflectors 14 and 15. That is, the region where the reflectors 14 and 15 are formed is a surface acoustic wave reflection region.

  The IDT electrode 11 and the reflectors 14 and 15 can be formed of an appropriate conductive material. The IDT electrode 11 and the reflectors 14 and 15 include, for example, metals such as Au, Cu, Ag, W, Ta, Pt, Ni, Mo, Al, Ti, Cr, Pd, Co, and Mn, and among these metals It can be formed of an alloy containing one or more of these as a main component. Moreover, the IDT electrode 11 and the reflectors 14 and 15 can also be comprised by the laminated body of the some electrically conductive film which consists of the said metal and an alloy.

  Specifically, in the present embodiment, as shown in FIG. 3, the electrode fingers 12a and 13a and the dummy electrode fingers 12b and 13b of the IDT electrode 11 and the reflectors 14 and 15 are the first conductive film. 18. The bus bars 12c and 13c of the IDT electrode 11 and a pad (not shown) connected to the IDT electrode 11 by a wiring (not shown) are stacked on the first conductive film 18 and the first conductive film 18. It is comprised by the laminated body with the 2nd electrically conductive film 19 which is. For this reason, the bus bars 12c and 13c, and the wirings and pads are thickened. As a result, the electrical resistance values of the bus bars 12c and 13c and the wirings and pads can be reduced, so that the loss can be reduced. In addition, the mechanical strength of the bus bars 12c and 13c and the wiring and pads can be increased.

  In the bus bars 12c and 13c, the second conductive film 19 may be stacked on at least a part of the first conductive film 18, and the second conductive film 19 is formed on the entire first conductive film 18. The conductive film 19 is not necessarily formed.

  Specifically, in the present embodiment, the first conductive film 18 includes a NiCr layer (thickness: 10 nm), a Pt layer (thickness: 33 nm), and a Ti layer (thickness: 10 nm) from the piezoelectric substrate 10 side. , An Al—Cu alloy layer (thickness: 130 nm) and a Ti layer (thickness: 10 nm) are formed by a laminated film laminated in this order. Thereby, a high reflection coefficient can be realized. On the other hand, the second conductive film 19 includes an Al—Cu alloy layer (thickness: 700 nm), a Ti layer (thickness: 600 nm), and an Al layer (thickness: 1140 nm) from the first conductive film 18 side. It is comprised by the laminated film laminated | stacked in order. In the present embodiment, the laminated body of the first and second conductive films 18 and 19 is formed thicker than the dielectric layer 16 described later.

  In addition, the formation method of the 1st and 2nd electrically conductive films 18 and 19 is not specifically limited, It can form by appropriate thin film formation methods, such as the lift-off method.

A dielectric layer 16 is formed on the piezoelectric substrate 10 so as to cover the IDT electrode 11 and the reflectors 14 and 15. The dielectric layer 16 is a layer formed for the purpose of improving the frequency temperature characteristics of the surface acoustic wave device 1, for example. When the dielectric layer 16 is a layer whose purpose is to improve the frequency temperature characteristics of the surface acoustic wave device 1, the dielectric layer 16 has a TCF with a sign different from the TCF of the piezoelectric substrate 10, or the piezoelectric substrate Although it has the same sign as the TCF of 10, it is preferable to have a TCF having an absolute value smaller than the absolute value of the TCF of the piezoelectric substrate 10. In the present embodiment, since the piezoelectric substrate 10 is composed of a LiNbO ₃ substrate having a negative TCF, the dielectric layer 16 preferably has a positive TCF. Therefore, the dielectric layer 16 is, for example, preferably made of SiO ₂ layer. However, in the present invention, the dielectric layer 16 is not limited to those made of SiO ₂ layer. The dielectric layer 16 may be made of, for example, Si ₃ N ₄ , SiON, SiC, Ta ₂ O ₅ , TiO ₂ , TiN, Al ₂ O ₃ , TeO ₂ or the like.

The thickness of the dielectric layer 16 is not particularly limited as long as the surface acoustic wave excited by the IDT electrode 11 can be used as the main mode, but the electrode fingers 12a and 13a of the IDT electrode 11 are not limited. The dummy electrode fingers 12b and 13b are preferably thick enough to be embedded in the dielectric layer 16. That is, the dielectric layer 16 is preferably thicker than the first conductive film 18 constituting the electrode fingers 12a and 13a and the dummy electrode fingers 12b and 13b of the IDT electrode 11. Thereby, an excellent frequency temperature characteristic can be realized. The thickness of the dielectric layer 16 can be, for example, about 20% to 50% in terms of the surface acoustic wave wavelength ratio. If the thickness of the dielectric layer 16 is too thick, the pass band is not formed well, and desired filter characteristics may not be realized. If the thickness of the dielectric layer 16 is too thin, the frequency temperature characteristics may not be sufficiently improved. In the present embodiment, specifically, the dielectric layer 16 is composed of a SiO ₂ film having a thickness of 620 nm.

  Although the formation method of the dielectric material layer 16 is not specifically limited, As a suitable formation method of the dielectric material layer 16, bias sputtering method is mentioned, for example. In the present embodiment, specifically, the dielectric layer 16 is formed by a bias sputtering method.

  In the present embodiment, a protective layer 17 is formed on the dielectric layer 16. The protective layer 17 covers the dielectric layer 16.

The protective layer 17 is preferably made of a material having a lower H ₂ O transmittance than the dielectric layer 16 and has moisture resistance. Further, the protective layer 17 is preferably made of a material having a faster acoustic velocity of the surface acoustic wave that propagates than the dielectric layer 16. This is because the frequency characteristic of the surface acoustic wave device 1 can be adjusted by adjusting the thickness of the protective layer 17 by etching the protective layer 17 or the like.

Specifically, the protective layer 17 is, for example, a single film made of SiO ₂ , SiN, Si ₃ N ₄ , SiON, SiC, Ta ₂ O ₅ , TiO ₂ , TiN, Al ₂ O ₃ , TeO ₂ or the like. It is preferable that it is composed of a laminated film. More specifically, in the present embodiment, the protective layer 17 is composed of a SiN film having a thickness of 20 nm. Accordingly, the moisture resistance of the surface acoustic wave device 1 is enhanced by the protective layer 17, and the frequency characteristics of the surface acoustic wave device 1 can be adjusted by adjusting the thickness of the protective layer 17.

  The thickness of the protective layer 17 is not particularly limited as long as the surface acoustic wave excited by the IDT electrode 11 can be used as the main mode. The thickness of the protective layer 17 can be, for example, about 0.2% to 5% in terms of the surface acoustic wave wavelength ratio. If the thickness of the protective layer 17 is too thick, the function of adjusting the frequency characteristics of the surface acoustic wave device may deteriorate. If the thickness of the protective layer 17 is too thin, the moisture resistance of the surface acoustic wave device may deteriorate.

  The formation method of the protective layer 17 is not specifically limited. The protective layer 17 can be formed by, for example, a sputtering method or a vapor deposition method.

  In the present embodiment, the non-intersecting region portion 16a (see FIG. 3) that is a portion formed in the non-intersecting region D of the dielectric layer 16 includes portions having different thicknesses in the intersecting width direction y. As described above, the non-crossing region D is a surface acoustic wave reflection region. Therefore, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, includes a portion having a different thickness in the intersecting width direction y. Specifically, the surface 16a1 of the non-intersecting region portion 16a has a portion extending in a direction inclined with respect to the surface 10a of the piezoelectric substrate 10 in the intersecting width direction y. For this reason, the thickness of the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, gradually changes in the intersecting width direction y. Therefore, spurious and ripple can be effectively suppressed, and excellent resonance characteristics and filter characteristics can be obtained.

  In the present embodiment, the intersecting region portion 16b, which is a portion formed in the intersecting region C of the dielectric layer 16, has a substantially uniform thickness in the intersecting width direction y. As described above, the intersection region C is a surface acoustic wave excitation region. Therefore, the intersecting region portion 16b, which is a portion formed in the surface acoustic wave excitation region of the dielectric layer 16, has a substantially uniform thickness in the intersecting width direction y. Specifically, the surface 16b1 of the intersecting region portion 16b is formed in parallel and flat with the surface 10a of the piezoelectric substrate 10. Therefore, low loss can be realized.

  Hereinafter, the effect of this embodiment will be described in detail based on examples.

  As an example, the surface acoustic wave device 1 described in the above embodiment was manufactured in the following manner.

First, the first and second conductive films 18 and 19 having the above-described film structure are formed on the piezoelectric substrate 10 made of a 127 ° Y-cut X-propagation LiNbO ₃ substrate by lift-off, whereby the IDT electrode 11 and the reflective Containers 14 and 15, wiring and pads were formed.

Next, a dielectric layer 16 made of a SiO ₂ film having a thickness of 620 nm was formed on the piezoelectric substrate 10 so as to cover the IDT electrode 11, the reflectors 14 and 15, the wiring, and the pads. The dielectric layer 16 was formed by bias sputtering. By forming the dielectric layer 16 by bias sputtering as in the present embodiment, it is difficult to form a gap between the dielectric layer 16 and the IDT electrode 11 or the like. Therefore, the highly reliable surface acoustic wave device 1 can be manufactured.

  In the process of forming the dielectric layer 16 by bias sputtering, film formation by material deposition proceeds, while etching of the film formed by Ar plasma also proceeds simultaneously. Since the film formation rate at which the film is formed is higher than the etching rate of the formed film, the dielectric layer 16 is formed. Here, the Ar plasma is shielded by the thick film portion around the thick film portion (hereinafter sometimes referred to as “thick film portion”) constituted by the first and second conductive films 18 and 19. Thus, etching of the formed film by Ar plasma is inhibited. As a result, the etching rate of the formed film decreases as it approaches the thick film portion, and the deposition rate increases. Here, in the present embodiment, the bus bars 12c and 13c are constituted by the first and second conductive films 18 and 19 and have thick film portions, so that the dielectric layer 16 is formed as the bus bars 12c and 13c are approached. The film rate increases. As a result, in the non-intersecting region D, the dielectric layer 16 is thickest in the vicinity of the bus bars 12c and 13c, and decreases from the bus bar 12c and 13c side in the intersecting width direction y toward the intersecting region C side. As a result, in the dielectric layer 16, the surface 16a1 of the non-intersecting region portion 16a has a shape having a portion extending in a direction inclined with respect to the surface 10a of the piezoelectric substrate 10 in the intersecting width direction y. The portion 16a includes portions having different thicknesses in the cross width direction y. For this reason, the thickness of the non-intersecting region portion 16a gradually changes in the intersecting width direction y. On the other hand, in the intersecting region C, the thickness of the intersecting region portion 16b of the dielectric layer 16 is substantially uniform, and the surface 16b1 of the intersecting region portion 16b is parallel and flat with the surface 10a of the piezoelectric substrate 10.

  In the bias sputtering method, the inclination angle of the surface 16a1 of the non-intersecting region portion 16a can be set to a desired size by changing parameters during film formation (sputter output and substrate bias output). For this reason, it is easy to form a desired thickness deviation in the dielectric layer 16. The sputter output affects the film formation rate. The substrate bias output affects the etching rate. As the substrate bias output is increased, the inclination angle of the surface 16a1 of the non-intersecting region 16a can be increased.

  In this example, the film thickness difference wavelength ratio of the dielectric layer 16 was 5.1%. The thickness difference wavelength ratio of the dielectric layer 16 is a numerical value obtained by normalizing the difference between the thickness of the dielectric layer 16 in the intersecting region C and the maximum thickness of the dielectric layer 16 in the non-intersecting region D by the wavelength of the surface acoustic wave. It is. In the present embodiment, the maximum thickness of the dielectric layer 16 in the non-intersecting region D is the thickness of the portion of the dielectric layer 16 that is closest to the bus bars 12c and 13c. The film thickness difference wavelength ratio of the dielectric layer 16 indicates the magnitude of the change in the thickness of the non-intersecting region portion 16a.

  Next, a protective layer 17 made of a SiN film having a thickness of 20 nm was formed on the dielectric layer 16 by a sputtering method.

  Finally, the surface acoustic wave device 1 according to the example was completed by removing the dielectric layer 16 and the protective layer 17 located on the pad bump formation region by etching.

  As a comparative example, a surface acoustic wave device 100 having a cross-sectional structure shown in FIG. Specifically, the IDT electrode 111 and the dielectric layer 116 were formed on the piezoelectric substrate 110 as in the above example. At this time, the dielectric layer 116 was formed by bias sputtering so that the entire thickness of the dielectric layer 116 was uniform in the cross width direction. That is, the surface of the dielectric layer 116 was made flat. Thereafter, a surface acoustic wave device 100 according to a comparative example was produced by forming a protective layer 117 in the same manner as in the above example. In the surface acoustic wave device 100 according to the comparative example, the film thickness difference wavelength ratio of the dielectric layer 116 is 0%.

  The surface acoustic wave device 1 according to the above embodiment and the surface acoustic wave device 100 according to the comparative example have different resonance frequencies and antiresonance frequencies so that the difference in electrical characteristics can be easily understood. Specifically, the surface acoustic wave device 1 according to the example has a resonance frequency of 1875.0 MHz and an anti-resonance frequency of 1931.6 MHz. The surface acoustic wave device 100 according to the comparative example has a resonance frequency of 1890.8 MHz and an anti-resonance frequency of 1949.0 MHz.

  Next, the impedance characteristics and return loss of the surface acoustic wave device 1 according to the above example and the surface acoustic wave device 100 according to the comparative example were measured. The results are shown in FIGS.

  As is apparent from the results shown in FIGS. 5 and 6, in the surface acoustic wave device 100 according to the comparative example, ripples are generated in the vicinity of 2032.5 MHz, which is higher than the antiresonance frequency. This ripple is caused by the main mode (Rayleigh wave), and is located at the upper end (the end on the high frequency side) of the stop band of the non-intersection region D, which is the reflection region of the surface acoustic wave. For this reason, when a ladder type surface acoustic wave filter is configured by using a 1-port surface acoustic wave resonator like the surface acoustic wave device 100 according to the comparative example as a series arm resonator or a parallel arm resonator, a 1 port type is obtained. The ripple in the surface acoustic wave resonator becomes a spurious located on the higher frequency side than the pass band, and the filter characteristics deteriorate. Further, in the surface acoustic wave duplexer having a transmission side filter and a reception side filter, and the pass band of the transmission side filter is located on the lower frequency side than the pass band of the reception side filter, this ladder type surface acoustic wave filter Is used as a transmission-side filter, ripples are generated in the reception-side filter, and the characteristics of the reception-side filter are deteriorated.

  On the other hand, in the surface acoustic wave device 1 according to the example, the magnitude of the ripple generated in the vicinity of 2010.3 MHz, which is higher in frequency than the antiresonance frequency, is different in the surface acoustic wave device 100 according to the comparative example. Smaller than the generated ripple. That is, in this embodiment, ripples are suppressed and excellent resonance characteristics are realized. From the above results, as in the surface acoustic wave device 1 according to this example, the non-intersecting region 16a of the dielectric layer 16, that is, the portion formed in the surface acoustic wave reflection region of the dielectric layer 16 is shown. In the cross width direction y, it can be seen that by providing portions with different thicknesses, ripples in the 1-port surface acoustic wave resonator can be suppressed, and excellent resonance characteristics can be obtained. It can also be seen that excellent filter characteristics can be realized by configuring a ladder-type surface acoustic wave filter or a surface acoustic wave duplexer using such a 1-port surface acoustic wave resonator.

  In addition, the following reasons can be considered as a reason for obtaining this effect.

  In general, when the thickness of the dielectric layer 16 covering the IDT electrode 11 is reduced, the stop band is widened, and when the thickness of the dielectric layer 16 is increased, the stop band is narrowed. This is because the speed of sound changes depending on the thickness of the dielectric layer 16.

  For this reason, as in the surface acoustic wave device 1 according to the present embodiment, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, is in the intersecting width direction y. In the case where portions having different thicknesses are included, the sound speed is distributed in the non-intersecting region 16a. As a result, the frequency position of the ripple is dispersed, and the ripple is considered to be reduced. For this reason, the distribution width in the intersecting width direction y of the thickness of the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, is large. It is preferable that the film thickness difference wavelength ratio is large.

  FIG. 7 shows the surface acoustic wave device 1 according to the present embodiment when the film thickness difference wavelength ratio of the dielectric layer 16 is 1.2%, 2.0%, 3.2%, and 5.1%. 5 is a graph showing impedance characteristics of the surface acoustic wave device 100 according to the comparative example in which the film thickness difference wavelength ratio of the dielectric layer 116 is 0%. FIG. 8 shows the surface acoustic wave device 1 according to the present embodiment when the thickness difference wavelength ratio of the dielectric layer 16 is 1.2%, 2.0%, 3.2%, and 5.1%. 4 is a graph showing the return loss of each surface acoustic wave device 100 according to a comparative example in which the film thickness difference wavelength ratio of the dielectric layer 116 is 0%.

  7 and 8, the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 1.2% is represented by Δ = 1.2%. The surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 2.0% is represented by Δ = 2.0%. The surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 3.2% is represented by Δ = 3.2%. The surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 5.1% is represented by Δ = 5.1%. The surface acoustic wave device 100 according to the comparative example in which the film thickness difference wavelength ratio of the dielectric layer 116 is 0% is represented by Δ = 0%.

  In FIGS. 7 and 8, the resonance frequency and the anti-resonance frequency are made different so that the difference in electrical characteristics between the surface acoustic wave devices can be easily understood. The resonant frequency of the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 1.2% is 1885.4 MHz, and the antiresonant frequency is 1946.1 MHz. The resonant frequency of the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 2.0% is 1893.5 MHz, and the anti-resonant frequency is 1956.4 MHz. The resonant frequency of the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 3.2% is 1880.3 MHz, and the antiresonant frequency is 1941.5 MHz. The resonant frequency of the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 5.1% is 1878.1 MHz, and the antiresonant frequency is 1937.5 MHz. The resonance frequency of the surface acoustic wave device 100 according to the comparative example in which the film thickness difference wavelength ratio of the dielectric layer 116 is 0% is 1891.90 MHz, and the anti-resonance frequency is 1952.38 MHz.

  From the results shown in FIGS. 7 and 8, in the surface acoustic wave device 100 according to the comparative example in which the film thickness difference wavelength ratio of the dielectric layer 116 is 0%, the vicinity of 208.33 MHz, which is on the higher frequency side than the antiresonance frequency. A large ripple has occurred. In the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 1.2%, a ripple is generated in the vicinity of 2020.67 MHz. In the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 2.0%, ripples are generated in the vicinity of 2036.00 MHz. In the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 3.2%, ripples are generated in the vicinity of 2021.33 MHz. In the surface acoustic wave device 1 in which the thickness difference wavelength ratio of the dielectric layer 16 is 5.1%, ripples are generated in the vicinity of 2020.00 MHz.

  However, in the surface acoustic wave device 1 according to this example, it can be seen that the ripple decreases as the film thickness difference wavelength ratio of the dielectric layer 16 increases.

In the above embodiment, the bus bars 12c and 13c are constituted by the first and second conductive films 18 and 19, and have a thick film portion, so that the non-intersecting region portion 16a of the dielectric layer 16 is utilized. However, in the present invention, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, is formed. The method of forming the portions so as to include portions having different thicknesses in the cross width direction y is not limited to this. For example, the bus bars 12c and 13c are constituted by the first conductive film 18, and a dielectric layer such as a SiO ₂ film is formed on the first conductive film 18 constituting the bus bars 12c and 13c. By controlling the etching rate at the time of forming the dielectric layer 16 by the bias sputtering method by the layer, the non-intersecting region portion 16a, which is a portion formed in the reflective region of the surface acoustic wave of the dielectric layer 16, You may form so that the part from which thickness differs in the cross width direction y may be included.

  Further, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16 by the etch back method using the sacrificial layer, is a portion having a different thickness in the intersecting width direction y. It can also be formed to include. Specifically, a resist is applied on the dielectric layer 16 formed by bias sputtering, RF sputtering without applying a substrate bias, DC sputtering, or the like. Thereafter, the dielectric layer 16 is etched together with the resist (resist etch back), whereby the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, is crossed in the width direction. In y, it can form so that the part from which thickness differs may be included.

  In the first embodiment, the entire surface 16a1 is the surface of the piezoelectric substrate 10 in the intersecting width direction y in the entire non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16. The example which extended in the direction inclined with respect to 10a, ie, the thickness deviation in the cross width direction y was formed in the whole non-cross | intersecting area | region part 16a was demonstrated. However, the present invention is not limited to this configuration. In the present invention, in a part of the non-intersecting region portion 16a of the dielectric layer 16, the surface 16a1 extends in a direction inclined with respect to the surface 10a of the piezoelectric substrate 10 in the intersecting width direction y, and in other portions, The surface 16a1 may extend in a direction parallel to the surface 10a of the piezoelectric substrate 10 in the intersecting width direction y. That is, a thickness deviation in the intersecting width direction y is formed in a part of the portion of the dielectric layer 16 formed in the surface acoustic wave reflection region, and is formed in the surface acoustic wave reflection region of the dielectric layer 16. Among other portions, the thickness may be constant in the cross width direction y in other portions.

  In the first embodiment, the thickness of the non-intersecting region portion 16a, which is the portion formed in the surface acoustic wave reflection region of the dielectric layer 16, is the thickness of the bus bars 12c and 13c in the intersecting width direction y. The example which becomes thick as it approaches a film part, ie, leaves | separates from the intersection area | region C was demonstrated. However, the present invention is not limited to this configuration. For example, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, may be formed so as to become thicker as it approaches the intersecting region C in the intersecting width direction y. Good. Even in such a case, the non-intersecting region portion 16a that is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16 includes a portion having a different thickness in the intersecting width direction y. As in the case of the first embodiment, ripples and spurious can be suppressed.

  In the first embodiment, the example in which the non-intersecting region portion 16a of the dielectric layer 16 is provided with portions having different thicknesses in the intersecting width direction y has been described. However, the present invention is not limited to this configuration. In the present invention, portions of the dielectric layer 16 where the reflectors 14 and 15 are formed may be provided with portions having different thicknesses in the cross width direction y. Similar to the non-intersecting region D, the region where the reflectors 14 and 15 are formed is a surface acoustic wave reflection region. Even in such a case, since the portion formed in the surface acoustic wave reflection region of the dielectric layer 16 includes a portion having a different thickness in the intersecting width direction y, ripples and spurious can be suppressed. it can.

  Hereinafter, modifications of the preferred embodiment of the present invention and other embodiments will be described. In the following description, members having substantially the same functions as those in the first embodiment are referred to by the same reference numerals, and description thereof is omitted.

(First modification)
FIG. 9 is a schematic cross-sectional view of a surface acoustic wave device 2 according to a first modification of the present invention.

  The surface acoustic wave device 2 according to the present modification has substantially the same configuration as the surface acoustic wave device 1 according to the first embodiment except for the shape of the dielectric layer 16.

  In the first embodiment, the example in which the thickness of the non-intersecting region portion 16a of the dielectric layer 16 gradually changes in the intersecting width direction y has been described. However, according to the present invention, the portion formed in the surface acoustic wave reflection region of the dielectric layer 16 such as the non-crossing region portion 16a which is a portion formed in the non-crossing region D of the dielectric layer 16 intersects. The configuration is not limited to the above as long as it includes portions having different thicknesses in the width direction y.

  For example, as shown in FIG. 9, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, may be formed in a step structure. Specifically, in this modification, the non-intersecting region portion 16a includes a first portion 16a2, a second portion 16a3, and a third portion 16a4. The first portion 16a2, the second portion 16a3, and the third portion 16a4 are provided in this order from the intersecting region C side in the intersecting width direction y. Steps are formed between the surface of the first portion 16a2 and the surface of the second portion 16a3, and between the surface of the second portion 16a3 and the surface of the third portion 16a4. As described above, the non-intersecting region portion 16a, which is a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, has a step structure, thereby forming portions having different thicknesses in the intersecting width direction y. It may be. Even in this case, the same effect as that of the first embodiment can be obtained.

  The dielectric layer 16 in the present modification can be formed by forming the dielectric layer 16 and then etching the dielectric layer 16 using an etching resistant mask such as a photosensitive resist.

(Second and third modifications)
FIG. 10 is a schematic plan view of a surface acoustic wave device 3 according to a second modification of the present invention. FIG. 11 is a schematic plan view of a surface acoustic wave device 4 according to a third modification of the present invention. 10 and 11, the drawing of the dielectric layer 16 and the protective layer 17 is omitted.

  In the first embodiment, the IDT electrode 11 has been described with respect to an example in which the cross width is weighted so that a plurality of maximum values of the cross width appear in the surface acoustic wave propagation direction x. However, in the present invention, the configuration of the IDT electrode 11 is not particularly limited.

  For example, as shown in FIG. 10, the IDT electrode 11 may be weighted in the cross width so that one maximum value of the cross width appears in the surface acoustic wave propagation direction x. Specifically, as shown in FIG. 10, the IDT electrode 11 has a maximum intersection width at the center in the surface acoustic wave propagation direction x, and the intersection width decreases toward the end in the surface acoustic wave propagation direction. The intersection width is weighted. Even in such a case, a portion formed in the surface acoustic wave reflection region of the dielectric layer 16, such as a non-crossing region portion 16a that is a portion formed in the non-crossing region D of the dielectric layer 16. However, since it is formed so as to include portions having different thicknesses in the intersecting width direction y, the same effect as in the first embodiment can be obtained.

  As shown in FIG. 11, the IDT electrode 11 may be a regular IDT electrode whose crossing width is constant in the surface acoustic wave propagation direction x. When the IDT electrode 11 is a regular IDT electrode, the region where the reflectors 14 and 15 are formed is a surface acoustic wave reflection region. For this reason, when the IDT electrode 11 is a regular IDT electrode, a portion of the dielectric layer 16 where the reflectors 14 and 15 are formed is provided with a portion having a different thickness in the cross width direction y. Thus, the same effect as in the first embodiment can be obtained.

  Moreover, the bus bars 12c and 13c may not be formed in a straight line. For example, the bus bars 12c and 13c may be formed in a shape such that the distance between the ends of the bus bars 12c and 13c and the envelopes A and B is substantially constant in the surface acoustic wave propagation direction x. In this case, the electrical resistance loss generated in the electrode fingers 12a and 13a and the dummy electrode fingers 12b and 13b can be reduced. Therefore, the return loss can be further reduced.

(Second Embodiment)
FIG. 12 is a schematic circuit diagram of the surface acoustic wave device 5 according to the second embodiment of the present invention.

  In the first embodiment, the preferred embodiment of the present invention has been described by taking the surface acoustic wave device 1 that is a one-port surface acoustic wave resonator as an example. However, the present invention is not limited to this configuration. The surface acoustic wave device according to the present invention may be, for example, a surface acoustic wave filter. In the second embodiment, a preferred embodiment of the present invention will be described by taking a surface acoustic wave device 5 as a ladder type surface acoustic wave filter as an example.

  As shown in FIG. 12, the surface acoustic wave device 5 of this embodiment includes an input terminal 31 and an output terminal 32. The input terminal 31 and the output terminal 32 are connected by a series arm 33. The series arm 33 is provided with a plurality of series arm resonators S1 to S7. Parallel arms 34a to 34c are connected between the serial arm 33 and the ground potential. Each parallel arm 34a-34c is provided with parallel arm resonators P1-P3. The parallel arm 34a and the parallel arm 34b are commonly connected to the ground potential via the inductor L1. An inductor L2 is connected between the parallel arm 34c and the ground potential.

  In the present embodiment, at least one of the series arm resonators S1 to S7 and the parallel arm resonators P1 to P3 is configured by the surface acoustic wave device 1 according to the first embodiment. Therefore, spurious and ripple are suppressed, and good filter characteristics can be obtained. The surface acoustic wave device as a ladder-type surface acoustic wave filter may have another circuit configuration.

(Third embodiment)
FIG. 13 is a schematic plan view of a surface acoustic wave device 6 according to a third embodiment of the present invention. In FIG. 13, drawing of the dielectric layer 16 and the protective layer 17 is omitted. In the third embodiment, a preferred embodiment of the present invention will be described by taking a surface acoustic wave device 6 as a longitudinally coupled resonator type surface acoustic wave filter as an example.

  As shown in FIG. 13, the surface acoustic wave device 6 of the present embodiment includes first and second longitudinally coupled resonator type surface acoustic wave filter units that are cascade-connected between an input terminal 41 and an output terminal 42. 43 and 44 are provided. Each of the first and second longitudinally coupled resonator-type surface acoustic wave filter units 43 and 44 includes a plurality of IDT electrodes. At least one of the plurality of IDT electrodes constituting the first and second longitudinally coupled resonator type surface acoustic wave filter units 43 and 44 is the surface acoustic wave device 1 according to the first embodiment. The IDT electrode 11 is configured in the same manner. Therefore, spurious and ripple are suppressed, and good filter characteristics can be obtained.

(Fourth embodiment)
FIG. 14 is a schematic circuit diagram of the surface acoustic wave device 7 according to the fourth embodiment of the present invention. In the first embodiment, the preferred embodiment of the present invention has been described by taking the surface acoustic wave device 1 that is a one-port surface acoustic wave resonator as an example. However, the present invention is not limited to this configuration. The surface acoustic wave device according to the present invention may be, for example, a surface acoustic wave duplexer. In the fourth embodiment, a preferred embodiment of the present invention will be described by taking a surface acoustic wave device 7 as a surface acoustic wave duplexer as an example.

  As shown in FIG. 14, the surface acoustic wave device 7 of the present embodiment includes an antenna terminal 52 connected to an antenna 51, first and second reception side signal terminals 53 a and 53 b, and a transmission side signal terminal 54. It has. A reception-side filter 55 is connected between the antenna terminal 52 and the first and second reception-side signal terminals 53a and 53b. A transmission filter 56 is connected between the antenna terminal 52 and the transmission signal terminal 54. The reception-side filter 55 and the transmission-side filter 56 are composed of surface acoustic wave filters, and at least one of IDT electrodes constituting the reception-side filter 55 and the transmission-side filter 56 is related to the first embodiment. The configuration is the same as the IDT electrode 11 of the surface acoustic wave device 1. When at least one of the IDT electrodes constituting the reception-side filter 55 is configured similarly to the IDT electrode 11 of the surface acoustic wave device 1 according to the first embodiment, the surface acoustic wave device 7 The receiving side filter characteristics can be improved. When at least one of the IDT electrodes constituting the transmission filter 56 is configured similarly to the IDT electrode 11 of the surface acoustic wave device 1 according to the first embodiment, the surface acoustic wave device 7 is used. The transmission side filter characteristics can be improved.

DESCRIPTION OF SYMBOLS 1-7 ... Surface acoustic wave device 10 ... Piezoelectric substrate 10a ... Surface 11 of piezoelectric substrate ... IDT electrode 12 ... First comb-like electrode 12a ... Electrode finger 12b ... Dummy electrode finger 12c ... Bus bar 13 ... Second comb tooth Electrode finger 13b ... Electrode finger 13b ... Dummy electrode finger 13c ... Busbar 14, 15 ... Reflector 16 ... Dielectric layer 16a ... Non-intersecting region portion 16a1 of dielectric layer ... Surface 16a2 of non-intersecting region portion of dielectric layer ... Dielectric The first portion 16a3 of the non-crossing region portion of the body layer ... The second portion 16a4 of the non-crossing region portion of the dielectric layer ... The third portion 16b of the non-crossing region portion of the dielectric layer ... The crossing region of the dielectric layer Part 16b1 ... Surface 17 of dielectric layer crossing region part ... Protective layer 18 ... First conductive film 19 ... Second conductive film 31 ... Input terminal 32 ... Output terminal 33 ... Series arms 34a to 34c ... Parallel arms 41 ... Input terminal 42 ... output terminals 43 and 44 First and second longitudinally coupled resonator type surface acoustic wave filters 51... Antenna 52... Antenna terminals 53 a and 53 b. First and second reception side signal terminals 54... Transmission side signal terminal 55. Transmission side filters A1, A3, B1, B3... First envelope portions A2, A4, B2, B4. Second envelope portions L1, L2. Inductors P1 to P3... Parallel arm resonators S1 to S7. Resonator

Claims (10)

A piezoelectric substrate;
An IDT electrode formed on the piezoelectric substrate;
A surface acoustic wave device comprising a dielectric layer formed on the piezoelectric substrate so as to cover the IDT electrode,
Each of the IDT electrodes has a plurality of electrode fingers and includes first and second comb-like electrodes that are interleaved with each other,
In the region where the IDT electrode is formed, the electrode finger of the first comb-shaped electrode and the electrode finger of the second comb-shaped electrode adjacent to the electrode finger are propagated by surface acoustic wave propagation. An intersecting region intersecting in an intersecting width direction perpendicular to the direction, an electrode finger of the first comb-shaped electrode, and an electrode finger of the second comb-shaped electrode adjacent to the electrode finger And a non-intersecting region that does not intersect in the intersecting width direction,
The surface acoustic wave device, wherein a non-crossing region portion, which is a portion formed in the non-crossing region of the dielectric layer, includes a portion having a different thickness in the crossing width direction. The IDT electrode is weighted for cross width,
The first comb-like electrode has a dummy electrode finger facing the tip of the electrode finger of the second comb-like electrode in the cross width direction,
The second comb-like electrode has a dummy electrode finger facing the tip portion of the electrode finger of the first comb-like electrode in the cross width direction,
The surface acoustic wave device according to claim 1, wherein the dummy electrode fingers of the first and second comb-like electrodes are arranged in a non-intersecting region.   3. The surface acoustic wave device according to claim 1, wherein the thickness of the non-intersecting region portion gradually changes in the intersecting width direction.   The surface acoustic wave device according to claim 3, wherein the surface of the non-intersecting region portion has a portion extending in a direction inclined with respect to the surface of the piezoelectric substrate in the intersecting width direction. The non-intersecting region portion includes a first portion and a second portion adjacent to the first portion in the intersecting width direction,
The surface acoustic wave device according to claim 1 or 2, wherein a step is formed between a surface of the first portion and a surface of the second portion.   The elasticity according to any one of claims 1 to 5, wherein a surface of the intersecting region portion, which is a portion formed in the intersecting region of the dielectric layer, is parallel and flat to the surface of the piezoelectric substrate. Surface wave device. Each of the first and second comb-like electrodes has a bus bar to which the plurality of electrode fingers are connected,
The plurality of electrode fingers are composed of a first conductive film,
The said bus-bar is comprised by the said 1st electrically conductive film and the 2nd electrically conductive film currently formed on the said 1st electrically conductive film, The Claim 1 characterized by the above-mentioned. Surface acoustic wave device. A pair of reflectors located on both sides of the surface acoustic wave propagation direction of the region where the IDT electrode is provided;
The reflector is covered by the dielectric layer;
The surface acoustic wave device according to any one of claims 1 to 7, wherein a portion of a region where the reflector of the dielectric layer is formed includes a portion having a different thickness in the intersecting width direction. A piezoelectric substrate;
An IDT electrode formed on the piezoelectric substrate;
A pair of reflectors located on both sides of the surface acoustic wave propagation direction of the region where the IDT electrode is provided;
A surface acoustic wave device comprising a dielectric layer formed on the piezoelectric substrate so as to cover the IDT electrode and the reflector,
Each of the IDT electrodes has a plurality of electrode fingers and includes first and second comb-like electrodes that are interleaved with each other,
In the region where the IDT electrode is formed, the electrode finger of the first comb-shaped electrode and the electrode finger of the second comb-shaped electrode adjacent to the electrode finger are propagated by surface acoustic wave propagation. Including intersecting areas intersecting in the direction of the intersecting width perpendicular to the direction,
The surface acoustic wave device, wherein a portion of the region where the reflector of the dielectric layer is formed includes a portion having a different thickness in the intersecting width direction.   The surface acoustic wave device according to claim 1, wherein the dielectric layer is formed by a bias sputtering method.

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