Patent Publication Number: US-9887686-B2

Title: Acoustic wave device, transceiver device, and mobile communication device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-231115, filed on Nov. 13, 2014, the entire contents of which are incorporated herein by reference. 
     FIELD 
     A certain aspect of the present invention relates to an acoustic wave device, a transceiver device, and a mobile communication device. 
     BACKGROUND 
     Mobile terminals such as mobile phones and mobile information terminals have rapidly diffused with the development of mobile communication systems. Smaller and more sophisticated mobile terminals have been developed. In addition, the number of frequency bands employed in a single mobile terminal has steadily increased due to, for example, the diffusion of Long Term Evolution (LTE). Acoustic wave devices are used for filters and duplexers provided to devices employed in the mobile terminals. As the acoustic wave device, employed is a Surface Acoustic Wave (SAW) device, a boundary acoustic wave device, or a Bulk Acoustic Wave (BAW) resonator. 
     Japanese Patent Application Publication No. 7-99420 discloses providing a shield layer in a substrate on which a chip including an acoustic wave element formed therein is mounted. 
     The provision of the shield layer in the substrate enables to reduce the leakage of a high-frequency signal from the chip. However, the shield layer and the ground of the acoustic wave chip are interconnected in the substrate in Japanese Patent Application Publication Nos. 7-99420 and 2003-273520. Thus, a high-frequency signal leaks from the chip through the ground. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided an acoustic wave device including: an acoustic wave chip including an acoustic wave element formed therein; a multilayered substrate including the acoustic wave chip mounted on an upper surface of the multilayered substrate; a first ground terminal formed on a lower surface of the multilayered substrate and electrically coupled to a ground electrode of the acoustic wave chip; a second ground terminal formed on the lower surface of the multilayered substrate; a signal terminal formed on the lower surface of the multilayered substrate and electrically coupled to a signal electrode of the acoustic wave chip; and a shield layer formed at least on the upper surface of the multilayered substrate, on the lower surface of the multilayered substrate, or between the lower surface and the upper surface of the multilayered substrate so as to overlap with at least a part of the acoustic wave chip, not electrically coupled to the first ground terminal in the multilayered substrate, and electrically coupled to the second ground terminal. 
     According to another aspect of the present invention, there is provided a transceiver device including: a mounting board; and the above acoustic wave device, wherein the first ground terminal and the second ground terminal are individually coupled to a ground of the mounting board. 
     According to another aspect of the present invention, there is provided a mobile communication device including: the above transceiver device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an acoustic wave device in accordance with a first comparative example; 
         FIG. 2  is a cross-sectional view of the acoustic wave device of the first comparative example; 
         FIG. 3A  is a plan view of an exemplary filter chip, and  FIG. 3B  is a plan view of a resonator; 
         FIG. 4A  is a plan view of another exemplary filter chip, and  FIG. 4B  is a cross-sectional view of a resonator; 
         FIG. 5  is a diagram illustrating pass characteristics of a duplexer; 
         FIG. 6  is a block diagram of an acoustic wave device in accordance with a second comparative example; 
         FIG. 7  is a cross-sectional view of the acoustic wave device of the second comparative example; 
         FIG. 8  is a block diagram of an acoustic wave device in accordance with a first embodiment; 
         FIG. 9A  is a cross-sectional view of the acoustic wave device of the first embodiment, and  FIG. 9B  is a cross-sectional view illustrating the acoustic wave device of the first embodiment mounted on a mounting board; 
         FIG. 10A  through  FIG. 10C  are cross-sectional views of duplexers in accordance with first through third variations of the first embodiment, respectively; 
         FIG. 11A  through  FIG. 11C  are cross-sectional views of duplexers in accordance with fourth through sixth variations of the first embodiment, respectively; 
         FIG. 12A  and  FIG. 12B  are cross-sectional views of duplexers in accordance with seventh and eighth variations of the first embodiment, respectively. 
         FIG. 13  is a cross-sectional view of a filter in accordance with a ninth variation of the first embodiment; 
         FIG. 14A  through  FIG. 14C  are schematic cross-sectional views illustrating tenth through twelfth variations of the first embodiment, respectively; 
         FIG. 15  is a cross-sectional view of a duplexer in accordance with a second embodiment; 
         FIG. 16A  and  FIG. 16B  are plan views (No. 1) of layers of a multilayered substrate in the second embodiment; 
         FIG. 17A  and  FIG. 17B  are plan views (No. 2) of the layers of the multilayered substrate in the second embodiment; 
         FIG. 18A  and  FIG. 18B  are plan views illustrating an exemplary mounting board on which the duplexer of the second embodiment is mounted; 
         FIG. 19  is a diagram illustrating isolation characteristics of the second embodiment and a third comparative example; and 
         FIG. 20  is a block diagram of a mobile communication device in accordance with a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A description will first be given of leakage of a high-frequency signal with use of a comparative example of a duplexer.  FIG. 1  is a block diagram of an acoustic wave device in accordance with a first comparative example. As illustrated in  FIG. 1 , a duplexer  110  includes a transmit filter  50  and a receive filter  52 . The transmit filter  50  is electrically connected between a common terminal Ant and a transmit terminal Tx. The receive filter  52  is electrically connected between the common terminal Ant and a receive terminal Rx. 
     The transmit filter  50  includes one or more series resonators S 11  through S 14  and one or more parallel resonators P 11  through P 13 . The series resonators S 11  through S 14  are connected in series between the common terminal Ant and the transmit terminal Tx. The parallel resonators P 11  through P 13  are connected in parallel between the common terminal Ant and the transmit terminal Tx. The ground of the transmit filter  50  is coupled to a ground terminal Gt. 
     The receive filter  52  includes one or more series resonators S 21  through S 24  and one or more parallel resonators P 21  through P 23 . The series resonators S 21  through S 24  are connected in series between the common terminal Ant and the receive terminal Rx. The parallel resonators P 21  through P 23  are connected in parallel between the common terminal Ant and the receive terminal Rx. The ground of the receive filter  52  is coupled to a ground terminal Gr. 
       FIG. 2  is a cross-sectional view of the acoustic wave device of the first comparative example. As illustrated in  FIG. 2 , the transmit filter  50  is formed in a transmit filter chip  30 , and the receive filter  52  is formed in a receive filter chip  32 . The chips  30  and  32  are mounted on a multilayered substrate  10 . The multilayered substrate  10  is formed by stacking layers  11  through  13 . The layers  11  through  13  are insulating layers such as ceramics or a resin. A conductive layer  21  is formed on the upper side of the layer  11 , a conductive layer  22  is formed on the upper side of the layer  12 , and a conductive layer  23  is formed on the upper side of the layer  13 . A conductive layer  20  is formed on the lower side of the layer  11 . Formed are penetrating vias  16  through  18  that respectively penetrate through the layers  11  through  13 . The conductive layers  20  through  23  and the penetrating vias  16  through  18  are made of a metal such as copper, gold, or aluminum. In the present description, the uppermost surface of the multilayered substrate  10  is referred to as the upper surface of the multilayered substrate  10 , and the lowermost surface of the multilayered substrate  10  is referred to as the lower surface of the multilayered substrate  10 . In addition, the upper surfaces of the layers  11  through  13  making up the multilayered substrate  10  are referred to as the upper sides of the layers  11  through  13 , and the lower surfaces of the layers  11  through  13  are referred to as the lower sides of the layers  11  through  13 . 
     The conductive layer  20  includes a transmit foot pad FTx, a receive foot pad FRx, a common foot pad, and ground foot pads FGt and FGr. The conductive layers  21  and  22  include lines. The conductive layer  23  includes a transmit electrode PTx, a receive electrode PRx, a common electrode, ground electrodes PGt and PGr, and a line. The illustration of the common foot pad and the common electrode is omitted. The chips  30  and  32  are mounted on the upper surface of the multilayered substrate  10 . A sealing portion  34  seals the chips  30  and  32 . The sealing portion  34  may not be formed on the lower surfaces of the chips  30  and  32 . The lower surfaces of the chips  30  and  32  are exposed to, for example, air-spaces  31 . 
       FIG. 3A  is a plan view of an exemplary filter chip, and  FIG. 3B  is a plan view of a resonator. As illustrated in  FIG. 3A , series resonators S 1  through S 4  and parallel resonators P 1  through P 3 , electrodes  38 , and lines  46  are formed on a piezoelectric substrate  40  as acoustic wave elements. The electrodes  38  include signal electrodes PS 1 , PS 2  and ground electrodes PG. The series resonators S 1  through S 4  are connected in series between the signal electrodes PS 1  and PS 2  through the lines  46 . The parallel resonators P 1  through P 3  are connected between the lines  46  connecting the series resonators S 1  through S 4  and the ground electrodes PG. The lines  46  and the electrodes  38  are formed of a metal film such as copper. 
     As illustrated in  FIG. 3B , the series resonators S 1  through S 4  and the parallel resonators P 1  through P 3  include an Interdigital Transducer (IDT)  49  formed on the piezoelectric substrate  40  and reflectors R 0  located at the both sides of the IDT  49 . The piezoelectric substrate  40  is, for example, a lithium tantalate substrate or a lithium niobate substrate. The IDT  49  and the reflectors R 0  are formed of a metal film such as aluminum or copper. As described above, a surface acoustic wave resonator, a boundary acoustic wave resonator, or a Love wave resonator can be used as a resonator. 
       FIG. 4A  is a plan view of another exemplary filter chip, and  FIG. 4B  is a cross-sectional view of a resonator. As illustrated in  FIG. 4A , on a substrate  45 , formed are the series resonators S 1  through S 4  and the parallel resonators P 1  through P 3 , the electrodes  38 , and the lines  46 . As illustrated in  FIG. 4B , each of the series resonators S 1  through S 4  and the parallel resonators P 1  through P 3  includes a lower electrode  41 , a piezoelectric film  42 , and an upper electrode  43  formed on the substrate  45 . A region where the lower electrode  41  and the upper electrode  43  face each other across the piezoelectric film  42  is a resonance region  44 . The lower electrode  41  in the resonance region  44  is exposed to an air-space  48 . The substrate  45  is, for example, a semiconductor substrate such as a silicon substrate or an insulating substrate such as a glass substrate. The lower electrode  41  and the upper electrode  43  are, for example, metal films such as a ruthenium film. The piezoelectric film  42  is, for example, an aluminum nitride film. Other configurations are the same as those of  FIG. 3A , and thus the description is omitted. 
     Back to  FIG. 2 , the chips  30  and  32  are, for example, the filter chips illustrated in  FIG. 3A  or  FIG. 4A . The chips  30  and  32  have dimensions of, for example, 0.7 mm×0.7 mm and a thickness of 0.15 mm. The electrodes  38  formed on the lower surfaces of the chips  30  and  32  are bonded to the conductive layer  20  on the multilayered substrate  10  by bumps  36 . The transmit electrode PTx and the receive electrode PRx are bonded to the signal electrode PS 1  or PS 2 . The ground electrodes PGt and PGr are bonded to the ground electrodes PG. The transmit foot pad FTx, the receive foot pad FRx, the ground foot pads FGt and FGr are electrically coupled to the transmit electrode PTx, the receive electrode PRx, and the ground electrodes PGt and PGr through the conductive layers  21  through  23  and the penetrating vias  16  through  18 , respectively. The transmit terminal Tx, the receive terminal Rx, the common terminal Ant, and the ground terminals Gt and Gr in  FIG. 1  correspond to the transmit foot pad FTx, the receive foot pad FRx, the common foot pad, and the ground foot pads FGt and FGr, respectively. 
       FIG. 5  is a diagram illustrating pass characteristics of a duplexer. The transmit filter  50  filters high-frequency signals in the transmit band from high-frequency signals supplied from the transmit terminal Tx, and outputs the filtered high-frequency signals to the common terminal Ant. The receive filter  52  filters high-frequency signals in the receive band from high-frequency signals supplied from the common terminal Ant, and outputs the filtered high-frequency signals to the receive terminal Rx. The center frequency F 1  of the transmit band differs from the center frequency F 2  of the receive band, and F 2  is greater than F 1  (F 2 &gt;F 1 ), for example. The transmit band does not overlap with the receive band. 
     Since the receive filter  52  has a high impedance in the transmit band, a high-frequency signal in the transmit band fails to be transmitted through the receive filter  52 . However, as indicated by an arrow  70  in  FIG. 1 , a high-frequency signal in the transmit band may leak from the transmit terminal Tx to the receive terminal Rx. The leakage of the high-frequency signal is mainly due to the leakage of a high-frequency signal from the chip  30  to the chip  32  through an insulating material (dielectric substance) in the multilayered substrate  10  as indicated by the arrow  70  in  FIG. 2 . Thus, isolation characteristics from the transmit terminal to the receive terminal deteriorate. The deterioration of isolation characteristics causes a high-frequency signal leaking from a power amplifier located anterior to the transmit terminal Tx to create distortion and/or interfere with a reception signal as a noise in a low noise amplifier located posterior to the receive terminal Rx. Therefore, the receiving sensitivity deteriorates, and satisfactory communication is disturbed. 
     A description will be given of a second comparative example that reduces the leakage of the high-frequency signal in the first comparative example.  FIG. 6  is a block diagram of an acoustic wave device in accordance with the second comparative example. As illustrated in  FIG. 6 , in a duplexer  112 , a shield layer  25  is located between the transmit filter  50  and the receive filter  52 . The shield layer  25  is electrically coupled to a ground terminal Gs. 
       FIG. 7  is a cross-sectional view of the acoustic wave device of the second comparative example. As illustrated in  FIG. 7 , a shield layer  27  is located on the upper side of the layer  12 , and a shield layer  28  is located on the upper side of the layer  13 . The shield layers  27  and  28  are electrically coupled to ground foot pads FGs through the penetrating vias  16  through  18 . The ground electrodes PGt and PGr, and the ground foot pads FGt and FGr that correspond to ground terminals are electrically coupled to the shield layers  27  and  28  through the penetrating vias  16  through  18 . Other structures are the same as those of the first comparative example, and thus the description is omitted. Supplying the shield layers  27  and  28  with a reference electric potential such as a ground potential enables to reduce the leakage of a high-frequency signal from the chip  30  to the chip  32  through the insulating material of the multilayered substrate  10 . 
     However, in the second comparative example, the grounds of the chips  30  and  32  are electrically coupled to the shield layers  27  and  28  in the multilayered substrate  10 . When via wirings between the shield layers  27  and  28  and the ground foot pad FGs are equivalent to an inductor, the shield layers  27  and  28  are not strongly grounded. Thus, as indicated by arrows  72  in  FIG. 6  and  FIG. 7 , a high-frequency signal leaks from the ground of the chip  30  to the ground of the chip  32  through the shield layers  27  and  28 . 
     A description will now be given of embodiments that reduce the leakage of a high-frequency signal from the chip  30  to the chip  32 . 
     First Embodiment 
       FIG. 8  is a block diagram of an acoustic wave device in accordance with a first embodiment. As illustrated in  FIG. 8 , in a duplexer  100 , the ground of the transmit filter  50  is electrically coupled to the first ground terminal Gt without electrically connecting to the shield layer  25  and the second ground terminal Gs. The ground of the receive filter  52  is electrically coupled to the first ground terminal Gr without electrically connecting to the shield layer  25  and the second ground terminal Gs. In the acoustic wave device, the first ground terminal Gt and the ground terminal Gr are not electrically coupled to the second ground terminal Gs. 
       FIG. 9A  is a cross-sectional view of the acoustic wave device of the first embodiment. As illustrated in  FIG. 9A , apertures  35  are formed in the shield layer  27 , and the ground electrodes PGt and PGr are coupled to the ground foot pads FGt and FGr without electrically making contact with the shield layer  27 . Other structures are the same as those of the first and second comparative examples, and thus the description is omitted. 
       FIG. 9B  is a cross-sectional view illustrating the acoustic wave device of the first embodiment mounted on a mounting board. As illustrated in  FIG. 9B , the duplexer  100  is mounted on a mounting board  74 . Terminals  76  are located on the upper surface of the mounting board  74 . The foot pads of the duplexer  100  are bonded to the terminals  76  by solder  78 . The mounting board  74  is, for example, a mother board or a daughter board. The ground foot pads FGt and FGr, which correspond to a first ground terminal, and the ground foot pad FGs, which corresponds to a second ground terminal, are individually coupled to a ground in the mounting board  74 . 
     In the first embodiment, the grounds of the transmit filter  50  and the receive filter  52  are not electrically coupled to the shield layer  25  (the shield layers  27  and  28  in  FIG. 9A ) in the multilayered substrate  10  or in the acoustic wave device (the duplexer  100 ). This configuration enables to reduce the leakage of a high-frequency signal from the transmit filter  50  to the ground of the receive filter  52  through the shield layer  25 . Therefore, the isolation characteristics are improved. 
       FIG. 10A  through  FIG. 10C  are cross-sectional views of duplexers in accordance with first through third variations of the first embodiment. As illustrated in  FIG. 10A , the shield layer  28  is located in the conductive layer  23  on the upper surface of the multilayered substrate  10 , and is not located in the conductive layers  20  through  22 . The apertures  35  are formed in the conductive layer  23 . The ground electrodes PGt and PGr are formed in the apertures  35 . As illustrated in  FIG. 10B , the shield layer  27  is located in the inner conductive layer  22  not exposed from the multilayered substrate  10 , and is not located in the conductive layer  20 ,  21 , or  23 . The apertures  35  are formed in the conductive layer  22 . The lines electrically connecting the ground electrodes PGt and PGr to the ground foot pads FGt and FGr are formed in the apertures  35 . As illustrated in  FIG. 10C , a shield layer  26  is located in the conductive layer  20  on the lower surface of the multilayered substrate  10 , and is not located in the conductive layers  21  through  23 . The apertures  35  are formed in the conductive layer  20 . The ground foot pads FGt and FGr are formed in the apertures  35 . When the shield layer  26  is located on the lower surface of the multilayered substrate  10 , the ground foot pad FGs and the shield layer  26  may be interconnected by a line, or at least a part of the shield layer  26  may be used as the ground foot pad FGs. Other structures are the same as those of the first embodiment, and thus the description is omitted. 
       FIG. 11A  through  FIG. 11C  are cross-sectional views of duplexers in accordance with fourth through sixth variations of the first embodiment. As illustrated in  FIG. 11A , the shield layer  27  is located in the conductive layer  22  inside the multilayered substrate  10 , and the shield layer  28  is located in the conductive layer  23  on the upper surface of the multilayered substrate  10 . As illustrated in  FIG. 11B , the shield layer  26  is located in the conductive layer  20  on the lower surface of the multilayered substrate  10 , and the shield layer  27  is located in the conductive layer  22  inside the multilayered substrate  10 . As illustrated in  FIG. 11C , the shield layer  26  is located in the conductive layer  20  on the lower surface of the multilayered substrate  10 , the shield layer  27  is located in the conductive layer  22  inside the multilayered substrate  10 , and the shield layer  28  is located in the conductive layer  23  on the upper surface of the multilayered substrate  10 . Other structures are the same as those of the first embodiment and its first through third variations, and thus the description is omitted. 
     As described in the first through third variations of the first embodiment, the shield layer may be formed in one conductive layer of the conductive layers  20  through  23 . As described in the fourth through sixth variations of the first embodiment, the shield layer may be formed in more than one conductive layer of the conductive layers  20  through  23 , or may be located in all conductive layers. 
       FIG. 12A  and  FIG. 12B  are cross-sectional views of duplexers in accordance with seventh and eighth variations of the first embodiment. As illustrated in  FIG. 12A , a sealing portion  34   a  is made of a metal such as solder. On the multilayered substrate  10 , located are an interchip electrode  37  and a circular electrode  39  formed from the conductive layer  23 . The interchip electrode  37  is formed between the chips  30  and  32 . The circular electrode  39  is formed in a circular shape so as to surround the chips  30  and  32 . The sealing portion  34   a  makes contact with and is electrically coupled to the interchip electrode  37  and the circular electrode  39 . The sealing portion  34   a  seals the chips  30  and  32  so that the lower surfaces of the chips  30  and  32  and the bumps  36  are exposed to the air-spaces  31 . A cover film  33   a  is formed to cover the sealing portion  34   a . The cover film  33   a  is a metal film such as a nickel film or an insulating film such as a silicon oxide film. The interchip electrode  37  and the circular electrode  39  are electrically coupled to the ground foot pad FGs through the shield layer  27 . The sealing portion  34   a  is thereby not electrically coupled to the ground foot pad FGr or FGt in the multilayered substrate  10 . Other structures are the same as those of the second variation of the first embodiment, and thus the description is omitted. 
     As illustrated in  FIG. 12B , a sealing portion  34   b  is an insulating material such as a resin. A cover film  33   b  is formed to cover the sealing portion  34   b . The cover film  33   b  is a metal film such as a gold film. The cover film  33   b  is electrically coupled to the circular electrode  39 . Other structures are the same as those of the seventh variation of the first embodiment, and thus the description is omitted. 
     As described in the fourth through sixth variations of the first embodiment, the formation of the shield layers in more than one conductive layer enables to further reduce the leakage of a high-frequency signal from the filter chip through the ground. In addition, as described in the seventh and eighth variations of the first embodiment, the sealing portion  34   a  or the cover film  33   b  may be electrically coupled to the shield layer in the multilayered substrate  10 . This structure prevents the filter chip  30  from interfering with the sealing portion  34   a  or the cover film  33   b  through the ground. 
       FIG. 13  is a cross-sectional view of a filter in accordance with a ninth variation of the first embodiment. As illustrated in  FIG. 13 , the filter chip  30  is flip-chip mounted on the multilayered substrate  10 . The filter chip  30  is, for example, the filter chip illustrated in  FIG. 3A  or  FIG. 4A . A signal electrode PSf and a ground electrode PGf are located in the conductive layer  23 . The signal electrode PS 1  or PS 2  of the filter chip  30  is bonded to the signal electrode PSf by the bump  36 . The ground electrode PG of the filter chip  30  is bonded to the ground electrode PGf by the bump  36 . The signal electrode PSf is electrically coupled to a signal foot pad FS. The ground electrode PGf is electrically coupled to the ground foot pad FG. Other structures are the same as those of the second variation of the first embodiment, and thus the description is omitted. 
     In the ninth variation of the first embodiment, the shield layer  27  is electrically separated from the ground of the filter chip  30  in the multilayered substrate  10 . This structure enables to reduce the leakage of a high-frequency signal from the filter chip  30  through the ground. Thus, the variation of the characteristics of the filter chip  30  due to the leakage of a high-frequency signal can be reduced. 
       FIG. 14A  through  FIG. 14C  are schematic cross-sectional views illustrating tenth through twelfth variations of the first embodiment. The details of the multilayered substrate, the sealing portion, and the like are not illustrated. As illustrated in  FIG. 14A , a triplexer of the tenth variation of the first embodiment includes three filter chips  30  mounted on the upper surface of the multilayered substrate  10 . As illustrated in  FIG. 14B , a quadplexer of the eleventh variation of the first embodiment includes four filter chips  30  mounted on the upper surface of the multilayered substrate  10 . As illustrated in  FIG. 14C , a multiplexer of the twelfth variation of the first embodiment includes more than one filter chip  30  mounted on the upper surface of the multilayered substrate  10 . As with in the first embodiment and its first through ninth variations, the shield layers  26  through  28  are formed in the multilayered substrate  10 . Other structures are the same as those of the first embodiment and its first through ninth variations, and thus the description is omitted. 
     As described in the tenth through twelfth variations of the first embodiment, a triplexer, a quadplexer, or a multiplexer may have the shield layer. 
     As described above, in the first embodiment and its variations, an acoustic wave chip (e.g., the filter chips  30  and  32 ) including an acoustic wave element formed therein is mounted on the upper surface of the multilayered substrate  10 . A first ground terminal (e.g., the ground foot pads FGr, FGt, and FGf) electrically coupled to the ground electrode of the acoustic wave chip (e.g., the ground electrode PG in  FIG. 3A  and  FIG. 4A ) is formed on the lower surface of the multilayered substrate  10 . A signal terminal (e.g., the transmit foot pad FTx, the receive foot pad FRx, and the signal foot pad FS) electrically coupled to the signal electrode of the acoustic wave chip (e.g., the signal electrodes PS 1  and PS 2  in  FIG. 3A  and  FIG. 4A ) is formed on the lower surface of the multilayered substrate  10 . The shield layers  26  through  28  are formed at least on the upper surface of the multilayered substrate  10 , on the lower surface of the multilayered substrate, or between the lower surface and the upper surface so as to overlap with at least a part of the acoustic wave chip. In the present description, if one object overlaps with another object, at least a part of one object covers or is covered by at least a part of another object when transparently viewed from a direction perpendicular to the upper surface or the lower surface of the multilayered substrate. The shield layers  26  through  28  are coupled to the second ground terminal without electrically connecting to the first ground terminal in the multilayered substrate  10  and in the acoustic wave device. That is to say, the shield layers  26  through  28  are electrically separated from the first ground terminal. 
     This configuration allows the shield layers  26  through  28  to block the leakage of a high-frequency signal from the acoustic wave chip. Furthermore, since the shield layers  26  through  28  are not electrically coupled to the ground of the acoustic wave chip in the multilayered substrate  10  or in the acoustic wave device, the leakage of a high-frequency signal through the ground can be reduced. 
     The shield layers  26  through  28  have the apertures  35 , and the first ground terminal and the acoustic wave chip are electrically interconnected through lines formed in the apertures  35  (e.g., the conductive layers  20  through  23  and the penetrating vias  16  through  18 ). This structure allows the shield layers  26  through  28  to have a large area, thereby further reducing the leakage of a high-frequency signal. 
     To reduce the leakage of a high-frequency signal from the acoustic wave chip, the distance between the lower surface of the acoustic wave chip and the upper surface of the shield layer is preferably small. For example, when the layers  11  through  13  of the multilayered substrate  10  have relative permittivities of approximately 4.9 to 9.0, the distance between the lower surface of the acoustic wave chip and the upper surface of the shield layer is preferably less than five times the wavelength of a high-frequency signal in the acoustic wave chip (e.g., the wavelength of the center frequency of a filter when the acoustic wave chip is a filter chip), and more preferably less than three times. 
     To reduce the distance between the lower surface of the acoustic wave chip and the upper surface of the shield layer, the shield layer  28  is preferably formed on the upper surface of the multilayered substrate  10 . In this structure, at least one of the ground electrodes PGt, PGr, PGf (pad) is formed in the aperture  35 . This structure allows the shield layer  28  to have a large area, and allows the shield layer  28  to be electrically separated from the ground electrodes PGt, PGr, and PGf. 
     The electrodes to be bonded to the chips  30  and  32  are formed on the upper surface of the multilayered substrate  10 , and thus it is difficult to make the area of the shield layer  28  large. Thus, the shield layer  27  is preferably located on the upper side of the conductive layer  22  that is located uppermost among the conductive layers inside the multilayered substrate  10 . This structure enables to make the area of the shield layer  27  large and to reduce the distances between the shield layer  27  and the chips  30  and  32 . 
     When more than one acoustic wave chip is mounted, the shield layer is preferably formed so as to overlap with a region between the acoustic wave chips. This structure enables to reduce the leakage of a high-frequency signal between the acoustic wave chips. Moreover, when more than one acoustic wave chip is mounted, the shield layer may be formed so as to overlap with the acoustic wave chips. This structure also enables to reduce the leakage of a high-frequency signal between the acoustic wave chips. 
     Furthermore, when the acoustic wave chips are the transmit filter chip  30  and the receive filter chip  32 , the leakage of a high-frequency signal from the transmit filter to the receive filter is reduced. Thus, the isolation characteristics from the transmit terminal to the receive terminal can be improved. 
     Second Embodiment 
     A second embodiment simulated isolation characteristics of a duplexer.  FIG. 15  is a cross-sectional view of a duplexer in accordance with the second embodiment. The multilayered substrate  10  includes the layers  11  and  13 . The conductive layer  22  is located on the upper side of the layer  11 , and the conductive layer  23  is located on the upper side of the layer  13 . The conductive layer  21  is located on the lower side of the layer  11 . On the multilayered substrate  10 , flip-chip mounted are the transmit filter chip  30  and the receive filter chip  32  with use of the bumps  36 . The transmit filter chip  30  and the receive filter chip  32  are sealed by the sealing portion  34  made of solder. A lid  47  is located on the upper surfaces of the transmit filter chip  30 , the receive filter chip  32 , and the sealing portion  34 . 
     A transmit filter for Band  7  is formed in the transmit filter chip  30 , and a receive filter for Band  7  is formed in the receive filter chip  32 . The transmit band of Band  7  is from 2500 MHz to 2570 MHz, the receive band of Band  7  is from 2620 MHz to 2690 MHz. The transmit filter is a surface acoustic wave filter illustrated in  FIG. 3A , and the receive filter is a piezoelectric thin film resonator filter illustrated in  FIG. 4A . 
       FIG. 16A  through  FIG. 17B  are plan views of the layers of the multilayered substrate  10  in the second embodiment.  FIG. 16A  is a plan view of the electrodes  38  (indicated by cross hatching), and transparently illustrates the chips  30  and  32 .  FIG. 16B  is a plan view of the upper side of the layer  13 , and illustrates the conductive layer  23  by cross hatching, the electrodes  38  by black circles, and the penetrating vias  18  by open circles.  FIG. 17A  is a plan view of the upper side of the layer  11 , and illustrates the conductive layer  22  by cross hatching, the penetrating vias  18  by black circles, and the penetrating vias  16  by open circles.  FIG. 17B  is a plan view of the lower side of the layer  11  transparently viewed from the above, and illustrates the conductive layer  20  by cross hatching, and the penetrating vias  16  by open circles. 
     As illustrated  FIG. 16A , the transmit filter chip  30  and the receive filter chip  32  are mounted on the upper side of the layer  13 . The electrodes  38  include the signal electrodes PS 1 , PS 2  and the ground electrode PG. As illustrated in  FIG. 16B , the conductive layer  23  is formed on the upper side of the layer  13 . The conductive layer  23  includes the circular electrode  39 , the transmit electrode PTx, the receive electrode PRx, the common electrode PAnt, and the ground electrodes PGt and PGr. The penetrating vias  18  are formed in the layer  13 . The signal electrodes PS 1 , PS 2  and the ground electrode PG of the transmit filter chip  30  are bonded to the transmit electrode PTx, the common electrode PAnt, and the ground electrode PGt, respectively. The signal electrodes PS 1 , PS 2  and the ground electrodes PG of the receive filter chip  32  are bonded to the receive electrode PRx, the common electrode PAnt, and the ground electrodes PGr, respectively. 
     As illustrated in  FIG. 17A , the conductive layer  22  is located on the upper side of the layer  11 . The conductive layer  22  includes the shield layer  27  and lines connecting the penetrating vias  16  and  18 . The apertures  35  are formed in the shield layer  27 . The lines coupled to the transmit electrode PTx, the common electrode PAnt, the common electrode PAnt, and the ground electrodes PGt and PGr are formed in the apertures  35 , and are not electrically coupled to the shield layer  27 . In the present description, if one object is electrically coupled to another object, two conductive objects are electrically conducted with each other, and if one object is not electrically coupled to another object, two conductive objects are not electrically conducted with each other. The circular electrode  39  of  FIG. 16B  is electrically coupled to the shield layer  27  through the penetrating vias  18 . 
     As illustrated in  FIG. 17B , the conductive layer  20  is formed on the lower side of the layer  11 . The conductive layer  20  includes foot pads. The penetrating vias  16  are coupled the corresponding foot pads. The transmit electrode PTx, the receive electrode PRx, the common electrode PAnt, and the ground electrodes PGt and PGr of  FIG. 16B  are electrically coupled to the transmit foot pad FTx, the receive foot pad FRx, the common foot pad FAnt, and the ground foot pads FGt and FGr through the penetrating vias  16  and  18 , respectively. The shield layer  27  is electrically coupled to the ground foot pads FGs through the penetrating vias  16 . 
     As described above, the ground electrodes PG of the transmit filter chip  30  and the receive filter chip  32  are not electrically coupled to the shield layer  27  in the multilayered substrate  10  or in the acoustic wave device. The ground foot pads FGt and FGr electrically coupled to the ground electrodes PG and the ground foot pads FGs electrically coupled to the shield layer  27  are electrically separated from each other, and individually formed. 
       FIG. 18A  and  FIG. 18B  are plan views illustrating a mounting board on which the duplexer of the second embodiment is to be mounted. As illustrated in  FIG. 18A , the terminals  76  are formed on the upper surface of the mounting board  74 . The foot pads of  FIG. 17B  are bonded to the corresponding terminals  76 . The ground foot pads FGt and FGr and the ground foot pads FGs are electrically coupled to a common ground in the mounting board  74 . 
     As illustrated in  FIG. 18B , a ground terminal  76   a  is formed on the upper surface of the mounting board  74 . The ground foot pads FGt and FGr corresponding to first ground terminals and the ground foot pad FGs corresponding to a second ground terminal are bonded to the ground terminal  76   a , and electrically interconnected through the ground terminal  76   a  of the mounting board. 
       FIG. 19  is a diagram illustrating isolation characteristics of the second embodiment and a third comparative example. The third comparative example fails to provide the shield layer  27  and the ground foot pad FGs. As illustrated in  FIG. 19 , the second embodiment improves the worst isolation values (i.e., minimum isolation values) in the transmit band and the receive band compared to the third comparative example. 
     In the second embodiment, the shield layer  27  and the ground terminals FGt and FGr are not electrically interconnected in the multilayered substrate  10  or in the acoustic wave device. This structure improves the isolation characteristics. To improve the isolation characteristics, the shield layer is preferably located near the chips  30  and  32 . For example, it may be considered to form a shield layer with the conductive layer  23  on the upper side of the layer  13 . However, pads to be bonded to the electrodes  38  of the chips  30  and  32  and the circular electrode  39  are formed on the upper side of the layer  13 . Thus, the area of the shield layer is small. To address this problem, the shield layer  27  is formed with the uppermost conductive layer  22  among the conductive layers except the conductive layer  23 . This structure enables to make the area of the shield layer  27  large, and to reduce the distances between the shield layer  27  and the chips  30  and  32 . Furthermore, the apertures  35  are formed in the shield layer  27 , and the lines connecting the chips  30  and  32  to the ground foot pads FTx and FRx are formed in the apertures  35 . This structure enables to make the area of the shield layer  27  larger. Accordingly, the isolation characteristics can be improved as illustrated in  FIG. 19 . 
     Third Embodiment 
     A third embodiment is an exemplary mobile communication device including any one of the duplexers of the first embodiment, the second embodiment, and their variations.  FIG. 20  is a block diagram of a mobile communication device in accordance with the third embodiment. As illustrated in  FIG. 20 , the mobile communication device includes a module  56  that is a transceiver device, an integrated circuit  58 , and an antenna  54 . The module  56  includes a diplexer  80 , switches  86 , duplexers  60 , and power amplifiers  66 . The diplexer  80  includes a low-pass filter (LPF)  82  and a high-pass filter (HPF)  84 . The LPF  82  is connected between terminals  81  and  83 . The HPF  84  is connected between terminals  81  and  85 . The terminal  81  is coupled to the antenna  54 . The LPF  82  passes signals with lower frequency of high-frequency signals transmitted and received by the antenna  54 , and suppresses signals with higher frequency. The HPF  84  passes signals with higher frequency of signals transmitted and received by the antenna  54 , and suppresses signals with lower frequency. 
     The switch  86  connects the terminal  83  to one of terminals  61 . The duplexer  60  includes a transmit filter  62  and a receive filter  64 . The transmit filter  62  is connected between terminals  61  and  63 . The receive filter  64  is connected between terminals  61  and  65 . The transmit filter  62  passes high-frequency signals in the transmit band, and suppresses other high-frequency signals. The receive filter  64  passes high-frequency signals in the receive band, and suppresses other high-frequency signals. The power amplifier  66  amplifies and outputs transmission signals to the terminal  63 . A low noise amplifier  68  amplifies and outputs reception signals to the terminal  65 . 
     The module  56  that is a transceiver device has the duplexer or the filter of the first embodiment, the second embodiment, or their variations as the duplexer  60 , or the filter  62  or  64 . The module  56  may include the power amplifier  66  and/or the low noise amplifier  68 . A mobile terminal device has the module  56 . 
     As described above, the acoustic wave device of the first embodiment, the second embodiment, or their variations can be coupled to the antenna  54 , and mounted on a motherboard together with the power amplifier  66  and other elements to form a transceiver device capable of transmitting or receiving communication signals. Furthermore, the transceiver device is installed in the mobile communication device to enable to achieve communication with low noise. 
     Although the embodiments of the present invention have been described in detail, it is to be understood that the various change, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.