Patent Publication Number: US-2021193592-A1

Title: Semiconductor device

Description:
TECHNICAL FIELD 
     The present disclosure relates to a semiconductor device provided with a semiconductor element, and more specifically, to a semiconductor device provided with a switching element as the semiconductor element. 
     BACKGROUND ART 
     Semiconductor devices with switching elements such as MOSFETs or IGBTs are conventionally known. An example of a semiconductor device that uses a MOSFET is disclosed in Patent Document 1. In the semiconductor device, a semiconductor element is bonded to a lead that constitutes a drain terminal. The semiconductor device has a metal piece connected to a source pad of the semiconductor element and to a lead that constitutes a source terminal. The metal piece, which is made of aluminum, allows for flowing a large amount of current through the semiconductor element. The metal piece also promotes heat dissipation from the semiconductor element, thereby reducing ON-resistance. 
     The inventor conducted a ΔT j  power cycle test to a device having a configuration similar to the semiconductor device disclosed in Patent Document 1, to find that cracking can occur in the bonding layer (such as solder) interposed between the source pad and the metal piece. This is due to the thermal stress generated because the coefficient of linear expansion of the metal piece is large as compared with the semiconductor element. Such cracking in the bonding layer can be prevented by changing the material for the metal piece to copper (of which coefficient of linear expansion is smaller than that of aluminum). However, conducting a ΔT j  power cycle test to such a configuration using copper revealed that the gate wire connected to the gate pad of the semiconductor element and a sense wire connected to the source pad can be detached from the semiconductor element due to the concentration of thermal stress. 
     TECHNICAL REFERENCE 
     Patent Document 
     Patent Document 1: JP-A-2008-294384 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     An object of the present disclosure is to provide a semiconductor device that reduces or eliminates the problems described above (cracking of a bonding layer or detachment of a wire) and provides a high reliability. 
     Means for Solving the Problems 
     The semiconductor device provided according to an aspect of the present disclosure includes: an insulating support member having a front surface; a first and a second conductive layer disposed on the front surface; a first semiconductor element having a first side facing the front surface and a second side facing away from the first side in a thickness direction of the insulating support member, where the first semiconductor element is provided with a first and a second electrode on the second side and a third electrode on the first side, and the third electrode is bonded for electrical connection to the first conductive layer; a first lead connected to the first electrode and the second conductive layer; a first detection conductor connected to the first electrode; and a first gate conductor connected to the second electrode. At least one of the first detection conductor and the first gate conductor has an end connected to the first semiconductor element, where the end has a coefficient of linear expansion smaller than a coefficient of linear expansion of the first conductive layer. 
     Preferably, each of the first detection conductor and the first gate conductor has a pillow part connected to the first semiconductor element and a wire part connected to the pillow part, and the pillow part has a coefficient of linear expansion smaller than the coefficient of linear expansion of the first conductive layer. 
     Preferably, the pillow part comprises: a first layer made of an alloy containing iron and nickel; and a pair of second layers made of a metal different from the first layer, and the first layer is disposed between the paired second layers in the thickness direction. 
     Preferably, the pillow part comprises a first layer made of a semiconductor material and a pair of second layers made of a metal, and the first layer is disposed between the paired second layers in the thickness direction. 
     Preferably, the first detection conductor comprises a metal piece, the first gate conductor comprises a pillow part connected to the first semiconductor element and a wire part connected to the pillow part, and each of the first detection conductor and the pillow part has a coefficient of linear expansion smaller than the coefficient of linear expansion of the first conductive layer. 
     Preferably, the first detection conductor comprises: a first layer made of an alloy containing iron and nickel; and a pair of second layers made of a metal different from the first layer, and the first layer is disposed between the paired second lavers in the thickness direction. 
     Preferably, each of the first detection conductor and the first gate conductor comprises a metal piece, and each of the first detection conductor and the first gate conductor has a coefficient of linear expansion smaller than the coefficient of linear expansion of the first conductive layer. 
     Preferably, the semiconductor device further comprises a first detection wiring layer to which the first detection conductor is connected and a first gate wiring layer to which the first gate conductor is connected, where the first detection wiring layer and the first gate wiring layer overlap with the front surface as viewed along the thickness direction. 
     Preferably, the first detection wiring layer and the first gate wiring layer are disposed on the front surface. 
     Preferably, the semiconductor device further comprises an insulating layer disposed on the first conductive layer, wherein the first detection wiring layer and the first gate wiring layer are disposed on the insulating layer. 
     Preferably, the semiconductor device further comprises: a second semiconductor element provided with a first electrode, a second electrode and a third electrode, where the third electrode is bonded for electrical connection to the second conductive layer; a second lead connected to the first electrode of the second semiconductor element; a second detection conductor connected to the first electrode of the second semiconductor element; and a second gate conductor connected to the second electrode of the second semiconductor element. At least one of the second detection conductor and the second gate conductor has an end connected to the second semiconductor element, and the end has a coefficient of linear expansion smaller than a coefficient of linear expansion of the second conductive layer. 
     Preferably, each of the second detection conductor and the second gate conductor comprises a pillow part connected to the second semiconductor element and a wire part connected to the pillow part, and the pillow part has a coefficient of linear expansion smaller than the coefficient of linear expansion of the second conductive layer. 
     Preferably, the second detection conductor comprises a metal piece, the second gate conductor comprises a pillow part connected to the second semiconductor element and a wire part connected to the pillow part, and each of the second detection conductor and the pillow part has a coefficient of linear expansion smaller than the coefficient of linear expansion of the second conductive layer. 
     Preferably, each of the second detection conductor and the second gate conductor comprises a metal piece, and each of the second detection conductor and the second gate conductor has a coefficient of linear expansion smaller than the coefficient of linear expansion of the second conductive layer. 
     Preferably, the semiconductor device further comprises: a second detection wiring layer to which the second detection conductor is connected; and a second gate wiring layer to which the second gate conductor is connected, where the second detection wiring layer and the second gate wiring layer overlap with the front surface as viewed along the thickness direction. 
     Preferably, the semiconductor device further comprises: a first input terminal electrically connected to the first conductive layer; a second input terminal electrically connected to the second lead; and an output terminal electrically connected to the second conductive layer, where each of the first input terminal and the second input terminal is spaced apart from the output terminal in a direction orthogonal to the thickness direction, and the second lead is connected to the second input terminal. 
     Preferably, the first input terminal and the second input terminal are spaced apart from each other in the thickness direction, and a part of the second input terminal overlaps with the first input terminal as viewed along the thickness direction. 
     Other features and advantages of the semiconductor device according to the present disclosure will become apparent from the detailed description given below with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a semiconductor device according to a first embodiment; 
         FIG. 2  is a plan view of the semiconductor device shown in  FIG. 1 ; 
         FIG. 3  is a plan view (seen through a sealing resin) of the semiconductor device shown in  FIG. 1 ; 
         FIG. 4  is a plan view of the semiconductor device shown in  FIG. 3  as seen through a second input terminal, a plurality of first leads and a plurality of second leads; 
         FIG. 5  is a bottom view of the semiconductor device shown in  FIG. 1 ; 
         FIG. 6  is a right side view of the semiconductor device shown in  FIG. 1 ; 
         FIG. 7  is a left side view of the semiconductor device shown in  FIG. 1 ; 
         FIG. 8  is a front view of the semiconductor device shown in  FIG. 1 ; 
         FIG. 9  is a sectional view taken along line IX-IX in  FIG. 3 ; 
         FIG. 10  is a sectional view taken along line X-X in  FIG. 3 . 
         FIG. 11  is a view showing a part (at or near a first semiconductor element) of  FIG. 3 ; 
         FIG. 12  is a sectional view taken along line XII-XII in  FIG. 11 ; 
         FIG. 13  is a sectional view taken along line XIII-XIII in  FIG. 11 ; 
         FIG. 14  is a view showing a part (at or near a second semiconductor element) of  FIG. 3 ; 
         FIG. 15  is a sectional view taken along line XV-XV in  FIG. 14 ; 
         FIG. 16  is a sectional view taken along line XVI-XVI in  FIG. 14 ; 
         FIG. 17  is a sectional view of a part (at or near a first semiconductor element) of a semiconductor device according to a first variation of the first embodiment; 
         FIG. 18  is a sectional view of a part (at or near a first semiconductor element) of the semiconductor device shown in  FIG. 17 ; 
         FIG. 19  is a plan view of a part (at or near a first semiconductor element seen through the sealing resin) of a semiconductor device according to a second variation of the first embodiment; 
         FIG. 20  is a sectional view taken along line XX-XX in  FIG. 19 ; 
         FIG. 21  is a plan view of a part (at or near a second semiconductor element seen through the sealing resin) of the semiconductor device shown in  FIG. 19 ; 
         FIG. 22  is a sectional view taken along line XXII-XXII in  FIG. 21 ; 
         FIG. 23  is a plan view of a part (at or near a first semiconductor element seen through the sealing resin) of a semiconductor device according to a third variation of the first embodiment; 
         FIG. 24  is a sectional view taken along line XXIV-XXIV in  FIG. 23 ; 
         FIG. 25  is a plan view of a part (at or near a second semiconductor element seen through the sealing resin) of the semiconductor device shown in  FIG. 23 ; 
         FIG. 26  is a sectional view taken along line XXVI-XXVI in  FIG. 25 ; 
         FIG. 27  is a plan view (seen through the sealing resin) of a semiconductor device according to a second embodiment; 
         FIG. 28  is a bottom view of the semiconductor device shown in  FIG. 27 ; 
         FIG. 29  is a sectional view taken along line XXIX-XXIX in  FIG. 27 ; 
         FIG. 30  is a sectional view taken along line XXX-XXX in  FIG. 27 ; 
         FIG. 31  is a view showing a part (at or near a first semiconductor element) of  FIG. 27 ; 
         FIG. 32  is a view showing a part (at or near a second semiconductor element) of  FIG. 27 ; 
         FIG. 33  is a plan view of a part (at or near a first semiconductor element seen through the sealing resin) of a semiconductor device according to a first variation of the second embodiment; 
         FIG. 34  is a plan view of a part (at or near a second semiconductor element seen through the sealing resin) of the semiconductor device shown in  FIG. 33 ; 
         FIG. 35  is a plan view of a part (at or near a first semiconductor element seen through the sealing resin) of a semiconductor device according to a second variation of the second embodiment; and 
         FIG. 36  is a plan view of a part (at or near a second semiconductor element seen through the sealing resin) of the semiconductor device shown in  FIG. 35 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Various embodiments and their variations according to the present disclosure are described below based on the drawings. 
     First Embodiment 
     A semiconductor device A 10  according to a first embodiment is described below based on  FIGS. 1-16 . 
     As shown in  FIGS. 3, 4, 9 and 10 , the semiconductor device A 10  includes an insulating support member (insulating substrate)  10 . In the illustrated example, the insulating support member  10  is made up of two substrates, i.e., a first substrate  10 A and a second substrate  10 B, but the present disclosure is not limited to such a configuration. The semiconductor device A 10  also includes a first conductive layer  20 A, a second conductive layer  20 B, a first detection wiring layer  21 A, a first gate wiring layer  22 A, a plurality of first semiconductor elements  40 A, a plurality of first leads  51 A, a plurality of first detection conductors  52 A and a plurality of first gate conductors  53 A. In addition to these, the semiconductor device A 10  includes a second detection wiring layer  21 B, a second gate wiring layer  22 B, a first input terminal  31  (see  FIGS. 4 and 10 ), a second input terminal  32  (see  FIGS. 3 and 10 ), an output terminal  33  (see  FIGS. 3, 4 and 10 ), a pair of detection terminals  34  (see  FIGS. 3 and 4 ), a pair of gate terminals  35 , a plurality of dummy terminals  36 , a plurality of second semiconductor elements  40 B, a plurality of second leads  51 B, a plurality of second detection conductors  52 B, a plurality of second gate conductors  533 , a sealing resin  60  and a metal substrate  69  (see  FIGS. 9 and 10 ). In the illustrated example, the metal substrate  69  includes two regions corresponding to the first substrate  10 A and the second substrate  10 B, respectively, but the present disclosure is not limited to such a configuration. The semiconductor device A 10  is a power converter (power module) in which the first semiconductor elements  40 A and the second semiconductor elements  40 B are MOSFETS, for example. The semiconductor device A 10  may be used for a driving source of a motor, an inverter device for various electric appliances, and a DC/DC converter, for example. In  FIG. 3 , the sealing resin  60  is illustrated as transparent for convenience of understanding. In  FIG. 4 , the second input terminal  32 , the first leads  51 A and the second leads  51 B, which are shown in  FIG. 3 , are also illustrated as transparent for convenience of understanding. In these figures, the sealing resin  60 , the second input terminals  32 , the first leads  51 A and the second leads  51 B are indicated by imaginary lines (two-dot chain lines). 
     In the description of the semiconductor device A 10 , the thickness direction of the insulating support member  10  is referred to as “thickness direction z”. A direction orthogonal to the thickness direction z is referred to as “first direction x”. The direction orthogonal to both the thickness direction z and the first direction x is referred to as “second direction y”. As shown in  FIGS. 1 and 2 , the semiconductor device A 10  is rectangular as viewed along the thickness direction z, i.e., as viewed in plan. The first direction x corresponds to the longitudinal direction of the semiconductor device A 10 . The second direction y corresponds to the widthwise direction of the semiconductor device A 10 . Also, in the description of the semiconductor device A 10 , for convenience of understanding, the side in the first direction x on which the first input terminal  31  and the second input terminal  32  are located is referred to as “first side in the first direction”. The side in the first direction x on which the output terminal  33  is located is referred to as “second side in the first direction x”. Note that the terms “thickness direction z”, “first direction x”, “second direction y”, “first side in the first direction x” and “second side in the first direction” are applied to the description of a semiconductor device A 20  given later. 
     As shown in  FIGS. 3, 9 and 10 , the first conductive layer  20 A, the second conductive layer  20 B and the metal substrate  69  are arranged on the insulating support member  10 . The insulating support member  10  is electrically insulating. The insulating support member  10  is made of a ceramic material that has a high thermal conductivity. Aluminum nitride (AlN) is an example of such a ceramic material. 
     As shown in  FIGS. 3, 9 and 10 , in the semiconductor device A 10 , the insulating support member  10  includes two substrates, i.e., the first substrate  10 A and the second substrate  10 B. The first substrate  10 A and the second substrate  10 B are spaced apart from each other in the first direction x. The first substrate  10 A is offset toward the first side in the first direction x. The second substrate  10 B is offset toward the second side in the first direction x. As viewed along the thickness direction z, each of the first substrate  10 A and the second substrate  10 B has a rectangular shape with its longer sides extending along the second direction y. Note that the configuration of the insulating support member  10  is not limited to this and may be constituted of a single substrate. 
     As shown in  FIGS. 9 and 10 , each of the first substrate  10 A and the second substrate  10 B has a front surface  101  and a back surface  102 . The front surface  101  faces the side in the thickness direction z on which the first conductive layer  20 A and the second conductive layer  20 B are arranged. The back surface  102  faces away from the front surface  101  in the thickness direction z. 
     As shown in  FIGS. 3, 9 and 10 , the first conductive layer  20 A is arranged on the front surface  101  of the first substrate  10 A (insulating support member  10 ). Along with the second conductive layer  20 B, the first input terminal  31 , the second input terminal  32  and the output terminal  33 , the first conductive layer  20 A forms a conduction path connecting the semiconductor elements  40 A and the second semiconductor elements  403  to the outside of the semiconductor device A 10 . The first conductive layer  20 A is made of a metal foil made of copper (Cu) or a copper alloy, for example. As viewed along the thickness direction z, the first conductive layer  20 A has a rectangular shape with its longer sides extending along the second direction y. In the example of the semiconductor device A 10 , the first conductive layer  20 A is formed of a single region, but in another example, the first conductive layer may be divided into a plurality of regions. The number of the regions and shape of the first conductive layer  20 A can be set freely. Note that the surface of the first conductive layer  20 A may be plated with silver (Ag). 
     As shown in  FIGS. 3, 9 and 10 , the first detection wiring layer  21 A is arranged on the front surface  101  of the first substrate  10 A. Thus, as viewed along the thickness direction z, the first detection wiring layer  21 A overlaps with the front surface  101 . The first detection wiring layer  21 A is offset toward the second side in the first direction x from the first conductive layer  20 A. The first detection wiring layer  21 A is in the form of a strip elongated in the second direction y. The first detection wiring layer  21 A may be made of the same metal foil as the first conductive layer  20 A, for example. Note that the surface of the first detection wiring layer  21 A may be plated with silver. 
     As shown in  FIGS. 3, 9 and 10 , the first gate wiring layer  22 A is arranged on the front surface  101  of the first substrate  10 A. Thus, as viewed along the thickness direction z, the first gate wiring layer  22 A overlaps with the front surface  101 . The first gate wiring layer  22 A is located between the first conductive layer  20 A and the first detection wiring layer  21 A in the first direction x. The first gate wiring layer  22 A is in the form of a strip elongated in the second direction y. The first gate wiring layer  22 A may be made of the same metal foil as the first conductive layer  20 A. Note that the surface of the first gate wiring layer  22 A may be plated with silver. 
     As shown in  FIGS. 3, 9 and 10 , the second conductive layer  20 B is arranged on the front surface  101  of the second substrate  10 B (insulating support member  10 ). The second conductive layer  20 B is made of a metal foil made of copper or a copper alloy, for example. As viewed along the thickness direction z, the second conductive layer  20 B has a rectangular shape with its longer sides extending along the second direction y. In the example of the semiconductor device A 10 , the second conductive layer  20 B is formed of a single region, but in another example, the second conductive layer may be divided into a plurality of regions. The number of the regions and shape of the second conductive layer  20 B can be set freely. Note that the surface of the second conductive layer  20 B may be plated with silver. 
     As shown in  FIGS. 3, 9 and 10 , the second detection wiring layer  21 B is arranged on the front surface  101  of the second substrate  10 B. Thus, as viewed along the thickness direction z, the second detection wiring layer  21 B overlaps with the front surface  101 . The second detection wiring layer  21 B is offset toward the first side in the first direction x from the second conductive layer  20 B. The second detection wiring layer  21 B is in the form of a strip elongated in the second direction y. The second detection wiring layer  21 B may be made of the same metal foil as the second conductive layer  20 B, for example. Note that the surface of the second detection wiring layer  21 B may be plated with silver. 
     As shown in  FIGS. 3, 9 and 10 , the second gate wiring layer  22 B is arranged on the front surface  101  of the second substrate  10 B. Thus, as viewed along the thickness direction z, the second gate wiring layer  22 B overlaps with the front surface  101 . The second gate wiring layer  22 B is located between the second conductive layer  20 B and the second detection wiring layer  21 B in the first direction x. The second gate wiring layer  22 B is in the form of a strip elongated in the second direction y. The second gate wiring layer  22 B may be made of the same metal foil as the second conductive layer  20 B. Note that the surface of the second gate wiring layer  22 B may be plated with silver. 
     As shown in  FIGS. 2-6 , the first input terminal  31  and the second input terminal  32  are located on the first side in the first direction x. DC power (voltage), which is the power to be converted, is input to the first input terminal  31  and the second input terminal  32 . The first input terminal  31  is the positive electrode (P terminal). The second input terminal  32  is the negative electrode (N terminal). As shown in  FIG. 10 , the second input terminal  32  is spaced apart from all of the first input terminal  31 , the first conductive layer  20 A and the second conductive layer  20 B in the thickness direction z. The first input terminal  31  and the second input terminal  32  are metal plates. The material for the metal plates is copper or a copper alloy. 
     As shown in  FIG. 4 , the first input terminal  31  has a first connecting part  311  and a first terminal part  312 . In the first input terminal  31 , the boundary between the first connecting part  311  and the first terminal part  312  is a surface extending along the second direction y and the thickness direction z and containing a first side surface  63 A (described later) of the sealing resin  60  located on the first side in the first direction x. The entirety of the first connecting part  311  is covered with the sealing resin  60 . The part of the first connecting part  311  offset toward the second side of in the first direction x is shaped like comb teeth. This comb-teeth-like part is bonded for electrical connection to the surface of the first conductive layer  20 A. Such bonding is performed by solder bonding or ultrasonic bonding, for example. Thus, the first input terminal  31  is electrically connected to the first conductive layer  20 A. 
     As shown in  FIGS. 4 and 5 , the first terminal part  312  extends from the sealing resin  60  toward the first side in the first direction x. As viewed along the thickness direction z, the first terminal part  312  is rectangular. Opposite sides of the first terminal part  312  in the second direction y are covered with the sealing resin  60 . Other portions of the first terminal part  312  are exposed from the sealing resin  60 . With such an arrangement, the first input terminal  31  is supported by both of the first conductive layer  20 A and the sealing resin  60 . 
     As shown in  FIG. 3 , the second input terminal  32  has a second connecting part  321  and a second terminal part  322 . As viewed along the thickness direction z, the boundary between the second connecting part  321  and the second terminal part  322  of the second input terminal  32  corresponds to the boundary between the first connecting part  311  and the first terminal part  312  of the first input terminal  31 . The second connecting part  321  is in the form of a strip elongated in the second direction y. 
     As shown in  FIGS. 2 and 3 , the second terminal part  322  extends from the sealing resin  60  toward the first side in the first direction x. As viewed along the thickness direction z, the second terminal part  322  is rectangular. Opposite sides of the second terminal part  322  in the second direction y are covered with the sealing resin  60 . Other portions of the second terminal part  322  are exposed from the sealing resin  60 . As shown in  FIGS. 3 and 4 , as viewed along the thickness direction z, the second terminal part  322  overlaps with the first terminal part  312  of the first input terminal  31 . As shown in  FIG. 10 , the second terminal part  322  is offset from the first terminal part  312  in the sense of the thickness direction z in which the front surface  101  of the insulating support member  10  faces. Note that in the example of the semiconductor device A 10 , the shape of the second terminal part  322  is the same as that of the first terminal part  312 . 
     As shown in  FIGS. 6 and 10 , an insulator  39  is interposed between the first terminal part  312  of the first input terminal  31  and the second terminal part  322  of the second input terminal  32  in the thickness direction z. The insulator  39  is a flat plate. The insulator  39  is electrically insulating and made of insulating paper, for example. As viewed along the thickness direction z, the entirety of the first input terminal  31  overlaps with the insulator  39 . In the second input terminal  32 , part of the second connecting part  321  and the entirety of the second terminal part  322  overlap with the insulator  39 , as viewed along the thickness direction z. These portions overlapping with the insulator  39  as viewed along the thickness direction z are in contact with the insulator  39 . The insulator  39  insulates the first input terminal  31  and the second input terminal  32  from each other. Parts of the insulator  39  (parts on the second side in the first direction x and opposite sides in the second direction y) are covered with the sealing resin  60 . 
     As shown in  FIGS. 3, 4 and 10 , the insulator  39  includes an interposed part  391  and an extension  392 . The interposed part  391  is located between the first terminal part  312  of the first input terminal  31  and the second terminal part  322  of the second input terminal  32  in the thickness direction z. The entirety of the interposed part  391  is sandwiched between the first terminal part  312  and the second terminal part  322 . The extension  392  extends from the interposed part  391  toward the first side in the first direction x beyond the first terminal part  312  and the second terminal part  322 . Thus, the extension  392  is offset from the first terminal part  312  and the second terminal part  322  toward the first side in the first direction x. Opposite sides of the extension  392  in the second direction y are covered with the sealing resin  60 . 
     As shown in  FIGS. 2-7  (excluding  FIG. 6 ), the output terminal  33  is located on the second side in the first direction x. The AC power (voltage) obtained by power conversion by the first semiconductor elements  40 A and the second semiconductor elements  40 B is outputted from the output terminal  33 . The output terminal  33  is a metal plate. The material for the metal plate is copper or a copper alloy. The output terminal  33  has a connecting part  331  and a terminal part  332 . The boundary between the connecting part  331  and the terminal part  332  is a surface extending along the second direction y and the thickness direction z and containing a first side surface  63 A (described later) of the sealing resin  60  located on the second side in the first direction x. The entirety of the connecting part  331  is covered with the sealing resin  60 . The connecting part  331  is provided with a comb-teeth portion  331 A on the first side in the first direction x. The comb-teeth portion  331 A is bonded for electrical connection to the surface of the second conductive layer  20 B. Such bonding is performed by solder bonding or ultrasonic bonding, for example. Thus, the output terminal  33  is electrically connected to the second conductive layer  20 B. As shown in  FIGS. 2-5 , the terminal part  332  extends from the sealing resin  60  toward the second side in the first direction x. As viewed along the thickness direction z, the terminal part  332  is rectangular. Opposite sides of the terminal part  332  in the second direction y are covered with the sealing resin  60 . Other portions of the terminal part  332  are exposed from the sealing resin  60 . With such an arrangement, the output terminal  33  is supported by both of the second conductive layer  20 B and the sealing resin  60 . 
     As shown in  FIGS. 3, 9 and 10 , the first semiconductor elements  40 A are bonded for electrical connection to the first conductive layer  20 A. The first semiconductor elements  40 A are arranged at predetermined intervals along the second direction y. The first semiconductor elements  40 A form an upper arm circuit of the semiconductor device A 10 . Also, as shown in  FIGS. 3, 9 and 10 , the second semiconductor elements  40 B are bonded for electrical connection to the second conductive layer  20 B. The second semiconductor elements  40 B are arranged at predetermined intervals along the second direction y. The second semiconductor elements  40 B form a lower arm circuit of the semiconductor device A 10 . The first semiconductor elements  40 A and the second semiconductor elements  40 B are in staggered arrangement along the second direction y. In the illustrated example of the semiconductor device A 10 , the semiconductor device A 10  includes four first semiconductor elements  40 A and four second semiconductor element  40 B. The number of the first semiconductor elements  40 A and second semiconductor elements  40 B is not limited to this and can be varied according to the performance required for the semiconductor device A 10 . 
     The first semiconductor elements  40 A and the second semiconductor elements  40 B are the same semiconductor elements. The semiconductor elements may be, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor) made by using a semiconductor material mainly composed of silicon carbide (SiC). Note that the first semiconductor elements  40 A and the second semiconductor elements  40 B are not limited to MOSFETs and may be field-effect transistors including MISFETs (Metal-Insulator-Semiconductor Field-Effect Transistor) or bipolar transistors such as IGBTs (Insulated Gate Bipolar Transistor). In the description of semiconductor device A 10 , it is assumed that the first semiconductor elements  40 A and the second semiconductor elements  40 B are n-channel MOSFETs. 
     As shown in  FIGS. 11 and 14 , each of the first semiconductor elements  40 A and the second semiconductor elements  40 B is rectangular as viewed along the thickness direction z (square in the semiconductor device A 10 ). As shown in  FIGS. 11-16 , each of the first semiconductor elements  40 A and the second semiconductor elements  40 B includes an element front surface  401 , an element back surface  402 , a first electrode  41 , a second electrode  42 , a third electrode  43  and an insulating film  44 . The element front surface  401  and the element back surface  402  face away from each other in the thickness direction z. Of these, the element front surface  401  faces the side that the front surface  101  of the insulating support member  10  faces. 
     As shown in  FIGS. 11-16 , the first electrode  41  is on the element front surface  401 , i.e., on the side that the front surface  101  of the insulating support member  10  faces in the thickness direction z. A source current flows from inside the first semiconductor element  40 A or the second semiconductor element  403  to the first electrode  41 . 
     As shown in  FIGS. 11, 13, 14 and 16 , the second electrode  42  is on the element front surface  401 , i.e., on the side that the front surface  101  of the insulating support member  10  faces in the thickness direction z. A gate voltage for driving the first semiconductor element  40 A or the second semiconductor element  403  is applied to the second electrode  42 . The size of the second electrode  42  is smaller than that of the first electrode  41 . In each of the first semiconductor elements  40 A, the second electrode  42  is offset toward one side in the second direction y (the side on which the pair of detection terminals  34 , the pair of gate terminals  35  and the dummy terminals  36  are located). In each of the second semiconductor elements  40 B, the second electrode  42  is offset toward the other side in the second direction v. 
     As shown in  FIGS. 12, 13, 15 and 16 , the third electrode  43  is on the element back surface  402 , i.e., on the side facing the front surface  101  of the insulating support member  10  in the thickness direction z. The third electrode  43  extends over the entirety of the element back surface  402 . A drain current flows through the third electrode  43  into the first semiconductor element  40 A or the second semiconductor element  40 B. The third electrode  43  of each of the first semiconductor elements  40 A is bonded for electrical connection to the first conductive layer  20 A with a conductive first bonding layer  29 . The first bonding layer  29  is made of a lead-free solder mainly composed of tin (Sn), for example. Thus, the third electrodes  43  of the first semiconductor elements  40 A are electrically connected to the first conductive layer  20 A. Also, the third electrode  43  of each of the second semiconductor elements  40 B is bonded for electrical connection to the second conductive layer  20 B with a first bonding layer  29 . Thus, the third electrodes  43  of the second semiconductor elements  40 B are electrically connected to the second conductive layer  20 B. 
     As shown in  FIGS. 11-16 , the insulating film  44  is on the element front surface  401 . The insulating film  44  is electrically insulating. As viewed along the thickness direction z, the insulating film  44  surrounds each of the first electrode  41  and second electrode  42 . The insulating film  44  may be made up of, for example, a silicon dioxide (SiO 2 ) layer, a silicon nitride (Si 3 N 4 ) layer and a polybenzoxazole (PBO) layer laminated in the mentioned order on the element front surface  401 . Note that, in the insulating film  44 , a polyimide layer may be used instead of the polybenzoxazole layer. 
     As shown in  FIGS. 3 and 9 , the first leads  51 A are connected to the first electrodes  41  of the first semiconductor elements  40 A and the second conductive layer  20 B. As viewed along the thickness direction z, each of the first leads  51 A is in the form of a strip elongated in the first direction x. The first leads  51 A are made of copper or a copper alloy. The end of each first lead  51 A on the first side in the first direction x is connected to the first electrode  41  of a respective first semiconductor element  40 A with a conductive second bonding layer  49 . The second bonding layer  49  is made of a lead-free solder mainly composed of tin (Sn) or baked silver, for example. The end of each first lead  51 A on the second side in the first direction x is connected to the second conductive layer  20 B with a first bonding layer  29 . Thus, the first electrodes  41  of the first semiconductor elements  40 A are electrically connected to the second conductive layer  20 B. 
     As shown in  FIGS. 3 and 10 , the second leads  51 B are connected to the first electrodes  41  of the second semiconductor elements  40 B and the second input terminal  32 . As viewed along the thickness direction z, each of the second leads  51 B is in the form of a strip elongated in the first direction x. The second leads  51 B are made of copper or a copper alloy. The end surface of each second lead  51 B on the first side in the first direction x is directly connected to the second connecting part  321  of the second input terminal  32 . Thus, the second leads  51 B are integral with the second input terminal  32 . The end of each second lead  51 B on the second side in the first direction x is connected to the first electrode  41  of a respective second semiconductor element  40 B with a second bonding layer  49 . Thus, the first electrodes  41  of the second semiconductor elements  40 B are electrically connected to the second input terminal  32 . 
     As shown in  FIGS. 3 and 11 , the first detection conductors  52 A are connected to the first electrodes  41  of the first semiconductor elements  40 A and the first detection wiring layer  21 A. Thus, the first electrodes  41  of the first semiconductor elements  40 A are electrically connected to the first detection wiring layer  21 A. As shown in  FIGS. 11 and 12 , each of the first detection conductors  52 A has a pillow part  521  and a wire part  522 . 
     As shown in  FIG. 12 , the pillow part  521  of each first detection conductor  52 A is connected to the first electrode  41  of a respective first semiconductor element  40 A with a second bonding layer  49 . As shown in  FIG. 11 , the pillow part  521  is rectangular as viewed along the thickness direction z. The pillow part  521  has a first layer  521 A and a pair of second layers  521 B. The first layer  521 A is made of an alloy containing iron (Fe) and nickel (Ni). Examples of the alloy include invar (Fe-36Ni), super invar (Fe-32Ni-5Co) and Kovar. The paired second layers  521 B are made of a metal. Examples of the metal include copper, a copper alloy, aluminum and an aluminum alloy. The first layer  521 A is sandwiched between the paired second layers  521 B in the thickness direction z. In this way, the pillow part  521  is a laminate of a plurality of metal layers in the thickness direction z. The ratio of the thickness t 1  of the first layer  521 A and the thickness t 2  of each second layer  521 B may be t 1 :t 2 =8:1, for example. The coefficient of linear expansion of the pillow part  521  having such a configuration is in a range of 0 to 8×10 −6 /° C. In contrast, the coefficient of linear expansion of the first conductive layer  20 A is about 16×10 −6 /° C. Thus, the coefficient of linear expansion of the pillow part  521  is smaller than that of the first conductive layer  20 A. Note that the first layer  521 A may be made of a semiconductor material. As the semiconductor material, use may be made of silicon (Si), which has a relatively low electrical resistivity. In such a case again, the coefficient of linear expansion of the pillow part  521  is smaller than that of the first conductive layer  20 A. 
     As shown in  FIG. 11 , the wire part  522  of each first detection conductor  52 A is connected to the pillow part  521  of the first detection conductor  52 A and the first detection wiring layer  21 A. The wire part  522  is inclined at an inclination angle α 1   a  with respect to the first direction x. The wire part  522  may be made of aluminum, an aluminum alloy, copper, a copper alloy or a clad material made by some combination of these. 
     As shown in  FIGS. 3 and 14 , the second detection conductors  52 B are connected to the first electrodes  41  of the second semiconductor elements  40 B and the second detection wiring layer  21 B. Thus, the first electrodes  41  of the second semiconductor elements  40 B are electrically connected to the second detection wiring layer  21 B. As shown in  FIGS. 14 and 15 , each of the second detection conductors  52 B has a pillow part  521  and a wire part  522 . The pillow part  521  of each second detection conductor  52 B is connected to the first electrode  41  of a respective second semiconductor element  403  with a second bonding layer  49 . The wire part  522  of each second detection conductor  52 B is connected to the pillow part  521  of the second detection conductor  52 B and the second detection wiring layer  21 B. The wire part  522  of the second detection conductor  52 B is inclined at an inclination angle α 1   b  with respect to the first direction x. Other configurations of the pillow part  521  and the wire part  522  of each second detection conductor  52 B are the same as those of the pillow part  521  and the wire part  522  of each first detection conductor  52 A, so that the description of such configurations is omitted. Note that the coefficient of linear expansion of the second conductive layer  20 B is generally equal to that of the first conductive layer  20 A. Thus, the coefficient of linear expansion of the pillow part  521  is smaller than that of the second conductive layer  20 B. 
     As shown in  FIGS. 3 and 11 , the first gate conductors  53 A are connected to the second electrodes  42  of the first semiconductor elements  40 A and the first gate wiring layer  22 A. Thus, the second electrodes  42  of the first semiconductor elements  40 A are electrically connected to the first gate wiring layer  22 A. As shown in  FIGS. 11 and 13 , each of the first gate conductors  53 A has a pillow part  531  and a wire part  532 . 
     As shown in  FIG. 13 , the pillow part  531  of each first gate conductor  53 A is connected to the second electrode  42  of a respective first semiconductor element  40 A with a second bonding layer  49 . As shown in  FIG. 11 , the pillow part  531  is rectangular as viewed along the thickness direction z. The pillow part  531  has a first layer  531 A and a pair of second layers  531 B. The first layer  531 A is made of an alloy containing iron and nickel. Examples of the alloy are the same as those for the first layer  521 A of the pillow part  521  of the first detection conductor  52 A. The paired second layers  531 B are made of a metal. Examples of the metal are the same as those for the second layers  521 B of the pillow part  521  of the first detection conductor  52 A. The first layer  531 A is sandwiched between the paired second layers  5318  in the thickness direction z. In this way, the pillow part  531  is a laminate of a plurality of metal layers in the thickness direction z. The ratio of the thickness t 1  of the first layer  531 A and the thickness t 2  of each second layer  531 B may be t 1 :t 2 =8:1, for example. The coefficient of linear expansion of the pillow part  531  having such a configuration is in a range of 0 to 8×10 −6 /° C. contrast, the coefficient of linear expansion of the second conductive layer  20 B is about 16×10 −6 /° C. Thus, the coefficient of linear expansion of the pillow part  531  is smaller than that of the second conductive layer  20 B. Note that the first layer  531 A may be made of a semiconductor material. The example of the semiconductor material is the same as that for the first layer  521 A of the pillow part  521  of the first detection conductors  52 A. In such a case again, the coefficient of linear expansion of the pillow part  531  is smaller than that of the second conductive layer  20 B. 
     As shown in  FIG. 11 , the wire part  532  of each first gate conductor  53 A is connected to the pillow part  531  of the first gate conductor  53 A and the first gate wiring layer  22 A. The wire part  532  of the first gate conductor  53 A is inclined at an inclination angle α 2   a  with respect to the first direction x. Examples of the material for the wire part  532  are the same as those for the wire part  522  of the first detection conductor  52 A. 
     As shown in  FIGS. 3 and 14 , the second gate conductors  533  are connected to the second electrodes  42  of the second semiconductor elements  40 B and the second gate wiring layer  22 B. Thus, the second electrodes  42  of the second semiconductor elements  40 B are electrically connected to the second gate wiring layer  228 . As shown in  FIGS. 14 and 16 , each of the second gate conductors  533  has a pillow part  531  and a wire part  532 . The pillow part  531  of each second detection conductor  533  is connected to the second electrode  42  of a respective second semiconductor element  403  with a second bonding layer  49 . The wire part  532  of each second gate conductor  53 B is connected to the pillow part  531  of the second gate conductor  53 B and the second gate wiring layer  22 B. The wire part  532  of the second gate conductor  538  is inclined at an inclination angle α 2   b  with respect to the first direction x. Other configurations of the pillow part  531  and the wire part  532  of each second gate conductor  53 B are the same as those of the pillow part  531  and the wire part  532  of each first gate conductor  53 A, so that the description of such configurations is omitted. Note that the coefficient of linear expansion of the second conductive layer  20 B is generally equal to that of the first conductive layer  20 A. Thus, the coefficient of linear expansion of the pillow part  531  is smaller than that of the second conductive layer  20 B. 
     As shown in  FIG. 3 , the pair of detection terminals  34 , the pair of gate terminals  35  and the dummy terminals  36  are adjacent to the insulating support member  10  in the second direction y. These terminals are arranged side by side along the first direction x. In the semiconductor device A 10 , all of the detection terminals  34 , the gate terminals  35  and the dummy terminals  36  are made from a same lead frame. 
     As shown in  FIG. 3 , of the pair of the detection terminals  34 , one is located adjacent to the first substrate  10 A and the other one adjacent to the second substrate  10 B. The voltage (corresponding to the source current) applied to the first electrodes  41  of the first semiconductor elements  40 A or the second semiconductor elements  40 B is detected from each of the detection terminals  34 . Each of the detection terminals  34  has a connecting part  341  and a terminal part  342 . The connecting part  341  is covered with the sealing resin  60 . Thus, the detection terminals  34  are supported by the sealing resin  60 . Note that the surface of the connecting part  341  may be plated with silver, for example. The terminal part  342  is connected to the connecting part  341  and exposed from the sealing resin  60  (see  FIG. 8 ). The terminal part  342  is L-shaped as viewed along the first direction x. 
     As shown in  FIG. 3 , the paired gate terminals  35  are located adjacent to the paired detection terminal  34  in the first direction x. To each of the gate terminals  35 , a gate voltage for driving the first semiconductor elements  40 A or the second semiconductor element  403  is applied. Each of the gate terminals  35  has a connecting part  351  and a terminal part  352 . The connecting part  351  is covered with the sealing resin  60 . Thus, the gate terminals  35  are supported by the sealing resin  60 . Note that the surface of the connecting part  351  may be plated with silver, for example. The terminal part  352  is connected to the connecting part  351  and exposed from the sealing resin  60  (see  FIG. 8 ). The terminal part  352  is L-shaped as viewed along the first direction x. 
     As shown in  FIG. 3 , the dummy terminals  36  are located opposite the detection terminals  34  with respect to the gate terminals  35  in the first direction x. In the example of the semiconductor device A 10 , six dummy terminals  36  are provided. Of these, three dummy terminals  36  are offset toward the first side in the first direction x. The remaining three dummy terminals  36  are offset toward the second side in the first direction x. Note that the number of the dummy terminals is not limited to this. Also, the semiconductor device A 10  may not include the dummy terminal  36 . Each of the dummy terminals  36  has a connecting part  361  and a terminal part  362 . The connecting part  361  is covered with the sealing resin  60 . Thus, the dummy terminals  36  are supported by the sealing resin  60 . Note that the surface of the connecting part  361  may be plated with silver, for example. The terminal part  362  is connected to the connecting part  361  and exposed from the sealing resin  60  (see  FIG. 8 ). As shown in  FIGS. 6 and 7 , the terminal part  362  is L-shaped as viewed along the first direction x. Note that the shape of the terminal parts  342  of the detection terminals  34  and the shape of the terminal parts  352  of the gate terminals  35  are the same as that of the terminal parts  362 . 
     As shown in  FIG. 3 , the semiconductor device A 10  further includes a pair of first wires  54 A and a pair of second wires  54 B. The first wires  54 A and the second wires  54 B are made of aluminum, for example. 
     As shown in  FIG. 3 , the first wires  54 A are connected to the first detection wiring layer  21 A or the second detection wiring layer  21 B and the detection terminals  34 . In the detection terminals  34 , the first wires  54 A are connected to the surfaces of the connecting parts  341 . Thus, one of the detection terminals  34  that is adjacent to the first substrate  10 A is electrically connected to the first electrodes  41  of the first semiconductor elements  40 A, whereas the other one of the detection terminals  34  that is adjacent to the second substrate  103  is electrically connected to the first electrodes  41  of the second semiconductor elements  40 B. 
     As shown in  FIG. 3 , the second wires  548  are connected to the first gate wiring layer  22 A or the second gate wiring layer  223  and the gate terminals  35 . In the gate terminals  35 , the second wires  54 B are connected to the surfaces of the connecting parts  351 . Thus, one of the gate terminals  35  that is adjacent to the first substrate  10 A is electrically connected to the second electrodes  42  of the first semiconductor elements  40 A, whereas the other one of the gate terminals  35  that is adjacent to the second substrate  10 B is electrically connected to the second electrodes  42  of the second semiconductor elements  40 B. 
     As shown in  FIGS. 9 and 10 , the sealing resin  60  covers the insulating support member  10 , the first conductive layer  20 A, the second conductive layer  20 B, the first semiconductor elements  40 A and the second semiconductor elements  40 B. The sealing resin  60  further covers the first leads  51 A, the second leads  51 B, the first detection conductors  52 A, the second detection conductors  52 B, the first gate conductors  53 A, the second gate conductors  533 , the first wires  54 A and the second wires  548 . The sealing resin  60  may be made of black epoxy resin, for example. As shown in  FIGS. 2 and 5-8 , the sealing resin  60  has a top surface  61 , a bottom surface  62 , a pair of first side surfaces  63 A, a pair of second side surfaces  638 , a plurality of third side surfaces  63 C, a plurality of fourth side surfaces  63 D, a plurality of beveled parts  638  and a plurality of mounting holes  64 . 
     As shown in  FIGS. 9 and 10 , the top surface  61  faces the side that the front surface  101  of the insulating support member  10  faces in the thickness direction z. The bottom surface  62  faces away from the top surface  61  in the thickness direction z. As shown in  FIG. 5 , the metal substrate  69  is exposed from the bottom surface  62 . The bottom surface  62  has a frame-like shape surrounding the metal substrate  69 . 
     As shown in  FIGS. 2 and 5-7 , the paired first side surfaces  63 A are connected to both of the top surface  61  and the bottom surface  62  and face in the first direction x. From the first side surface  63 A on the first side in the first direction x, the first terminal part  312  of the first input terminal  31  and the second terminal part  322  of the second input terminal  32  extend toward the first side in the first direction x. From the first side surface  63 A on the second side in the first direction x, the terminal part  332  of the output terminal  33  extends toward the second side in the first direction x. In this way, part of each of the first input terminal  31  and the second input terminal  32  is exposed from the sealing resin  60  on the first side in the first direction x. Also, part of the output terminal  33  is exposed from the sealing resin  60  on the second side in the first direction x. 
     As shown in  FIGS. 2 and 5-8 , the paired second side surfaces  633  are connected to both of the top surface  61  and the bottom surface  62  and face in the second direction y. From one of the second side surfaces  633  are exposed the terminal parts  342  of the detection terminals  34 , the terminal parts  352  of the gate terminals  35  and the terminal parts  362  of the dummy terminals  36 . 
     As shown in  FIGS. 2 and 5-7 , the third side surfaces  63 C are connected to both of the top surface  61  and the bottom surface  62  and face in the second direction y. The third side surfaces  63 C include a pair of third side surfaces  63 C located on the first side in the first direction x and a pair of third side surfaces  63 C located on the second side in the first direction x. In each of the first side and the second side in the first direction x, the paired third side surfaces  63 C face each other in the second direction y. Also, in each of the first side and the second side in the first direction x, the paired third side surfaces  63 C are connected to opposite ends of the relevant first side surface  63 A in the second direction y. 
     As shown in  FIGS. 2 and 5-8 , the fourth side surfaces  63 D are connected to both of the top surface  61  and the bottom surface  62  and face in the first direction x. In the first direction x, the fourth side surfaces  63 D are offset from the first side surfaces  63 A toward the outside of the semiconductor device A 10 . The fourth side surfaces  63 D include a pair of fourth side surfaces  63 D located on the first side in the first direction x and a pair of fourth side surfaces  63 D located on the second side in the first direction x. In each of the first side and the second side in the first direction x, the opposite ends of each fourth side surface  63 D in the second direction y are connected to the relevant second side surface  63 E and the relevant third side surface  63 C. 
     As shown in  FIGS. 2 and 5 , each of the beveled parts  63 E is located at the boundary between a first side surface  63 A and a third side surface  63 C. As viewed along the thickness direction z, the beveled parts  63 E are inclined with respect to both of the first direction x and the second direction y. 
     As shown in  FIG. 9 , the mounting holes  64  penetrate the sealing resin  60  from the top surface  61  to the bottom surface  62  in the thickness direction z. The mounting holes  64  are used in attaching the semiconductor device A 10  to a heat sink (not shown). As shown in  FIGS. 2 and 5 , the edge of the mounting holes  64  is circular as viewed along the thickness direction z. The mounting holes  64  are located at the four corners of the sealing resin  60  as viewed along the thickness direction z. 
     As shown in  FIGS. 9 and 10 , the metal substrate  69  is provided on the entirety of the back surface  102  of the insulating support member  10  (the first substrate  10 A and the second substrate  10 B). Accordingly, the metal substrate  69  includes two region spaced apart from each other in the first direction x. As shown in  FIG. 5 , the metal substrate  69  is exposed from the bottom surface  62  of the sealing resin  60 . The metal substrate  69  is made of a metal foil made of copper (Cu) or a copper alloy, for example. The metal substrate  69  is used in attaching the semiconductor device A 10  to a heat sink, along with the mounting holes  64  of the sealing resin  60 . 
     First Variation of the First Embodiment 
     A semiconductor device A 11 , which is the first variation of the semiconductor device A 10 , is described below based on  FIGS. 17 and 18 . The semiconductor device A 11  differs from the semiconductor device A 10  in configuration of the pillow parts  521  of the first detection conductors  52 A and the second detection conductors  52 B and the pillow parts  531  of the first gate conductors  53 A and the second gate conductors  53 B. 
     As shown in  FIG. 17 , the first layer  521 A of the pillow part  521  of each first detection conductor  52 A has a lower layer portion  521 C, an upper layer portion  521 D and a frame surface  521 E. The lower layer portion  521 C is located on the lower side of the first layer  521 A. The second layer  521 B located at the lower end of the pillow part  521  adjoins the lower layer portion  521 C. The upper layer portion  521 D is connected to the upper end of the lower layer portion  521 C. As viewed along the thickness direction z, the area of the upper layer portion  521 D is larger than that of the lower layer portion  521 C. The second layer  521 B located at the upper end of the pillow part  521  adjoins the upper layer portion  521 D. Thus, as viewed along the thickness direction z, the second layer  521 B adjoining the upper layer portion  521 D has a larger area than the other second layer  521 B adjoining the lower layer portion  521 C. The frame surface  521 E faces the first electrode  41  of the first semiconductor element  40 A. As viewed along the thickness direction z, the frame surface  521 E surrounds the entire periphery of the lower layer portion  521 C. Though the illustration is omitted, the first layer  521 A of the pillow part  521  of each second detection conductor  528  also has a lower layer portion  521 C, an upper layer portion  521 D and a frame surface  521 E. These have the same configurations as the lower layer portion  521 C, the upper layer portion  521 D and the frame surface  521 E of the pillow part  521  of the first detection conductors  52 A, so that the description is omitted. 
     As shown in  FIG. 18 , the first layer  531 A of the pillow part  531  of each first gate conductor  53 A has a lower layer portion  531 C, an upper layer portion  531 D and a frame surface  531 E. The lower layer portion  531 C is located on the lower side of the first layer  531 A. The second layer  531 B located at the lower end of the pillow part  531  adjoins the lower layer portion  531 C. The upper layer portion  531 E is connected to the upper end of the lower layer portion  531 C. As viewed along the thickness direction z, the area of the upper layer portion  531 D is larger than that of the lower layer portion  531 C. The second layer  531 B located at the upper end of the pillow part  531  adjoins the upper layer portion  531 B. Thus, as viewed along the thickness direction z, the second layer  531 B adjoining the upper layer portion  531 D has a larger area than the other second layer  531 B adjoining the lower layer portion  531 C. The frame surface  531 E faces the second electrode  42  of the first semiconductor element  40 A. As viewed along the thickness direction z, the frame surface  531 E surrounds the entire periphery of the lower layer portion  531 C. Though the illustration is omitted, the first layer  531 A of the pillow part  531  of each second gate conductor  53 B also has a lower layer portion  531 C, an upper layer portion  531 D and a frame surface  531 E. These have the same configurations as the lower layer portion  531 C, the upper layer portion  531 D and the frame surface  531 E of the pillow part  531  of the first gate conductors  53 A, so that the description is omitted. 
     Second Variation of the First Embodiment 
     A semiconductor device A 12 , which is the second variation of the semiconductor device A 10 , is described below based on  FIGS. 19-22 . The semiconductor device Alt differs from the semiconductor device A 10  in configuration of the first detection conductors  52 A and the second detection conductors  52 B. 
     As shown in  FIG. 19 , as viewed along the thickness direction z, each of the first detection conductors  52 A is in the form of a strip elongated in the first direction x. The width B 1   a  of the first detection conductors  52 A is smaller than the width Ba of the first leads  51 A. Each first detection conductor  52 A is made of an elongated metal piece (metal strip). As shown in  FIG. 20 , the end of each first detection conductor  52 A on the first side in the first direction x is connected to the first electrode  41  of a respective first semiconductor element  40 A with a second bonding layer  49 . The end of each first detection conductor  52 A on the second side in the first direction x is connected to the first detection wiring layer  21 A with a first bonding layer  29 . 
     As shown in  FIG. 20 , each of the first detection conductors  52 A has a has a first layer  523  and a pair of second layers  524 . The first layer  523  is made of an alloy containing iron and nickel. Examples of the alloy are the same as those for the first layer  521 A of the pillow part  521  of the first detection conductor  52 A. The paired second layers  524  are made of a metal. Examples of the metal are the same as those for the paired second layers  521 B of the pillow part  521  of the first detection conductor  52 A. The first layer  523  is sandwiched between the paired second layers  524  in the thickness direction z. In this way, the first detection conductor  52 A is a laminate of a plurality of metal layers in the thickness direction z. The ratio of the thickness t 3   a  of the first layer  523  at the end on the first side in the first direction x and the thickness t 4   a  of the first layer  523  at the end on the second side in the first direction x may be t 3   a :t 4   a= 1:2, for example. The coefficient of linear expansion of the first detection conductor  52 A having such a configuration is in a range of 0 to 8×10 −6 /° C. In contrast, the coefficient of linear expansion of the first conductive layer  20 A is about 16×10 6 /° C. Thus, the coefficient of linear expansion of the first detection conductors  52 A is smaller than that of the first conductive layer  20 A. The first layer  523  of the first detection conductor  52 A has a transitional surface  523 A. The transitional surface  523 A is a curved surface located at the section where the thickness of the first layer  523  changes from the thickness t 3   a  to the thickness t 4   a.    
     As shown in  FIG. 21 , as viewed along the thickness direction z, each of the second detection conductors  52 B is in the form of a strip elongated in the first direction x. The width B 1   b  of the second detection conductors  52 B is smaller than the width Bb of the second leads  51 B. Each second detection conductor  52 B is made of a metal piece. As shown in  FIG. 22 , the end of each second detection conductor  52 B on the first side in the first direction x is connected to the second detection wiring layer  21 B with a first bonding layer  29 . The end of each second detection conductor  52 B on the second side in the first direction x is connected to the first electrode  41  of a respective second semiconductor element  403  with a second bonding layer  49 . 
     As shown in  FIG. 22 , each of the second detection conductors  52 B has a has a first layer  523  and a pair of second layers  524 . The ratio of the thickness t 3   b  of the first layer  523  at the end on the first side in the first direction x and the thickness t 4   b  of the first layer  523  at the end on the second side in the first direction x may be t 3   b :t 4   b= 2:1, for example. Other configurations of the first layer  523  and the second layers  524  of each second detection conductor  528  are the same as those of the first layer  523  and the second layers  524  of each first detection conductor  52 A, so that the description of such configurations is omitted. Note that the coefficient of linear expansion of the second conductive layer  20 B is generally equal to that of the first conductive layer  20 A. Thus, the coefficient of linear expansion of the second detection conductor  528  is smaller than that of the second conductive layer  20 B. The first layer  523  of the second detection conductor  528  has a transitional surface  523 A. The transitional surface  523 A is a curved surface located at the section where the thickness of the first layer  523  changes from the thickness t 3   b  to the thickness t 4   b.    
     Third Variation of the First Embodiment 
     A semiconductor device A 13 , which is the third variation of the semiconductor device A 10 , is described below based on  FIGS. 23-26 . The semiconductor device A 13  differs from the semiconductor device A 10  in configuration of the first detection conductors  52 A, the second detection conductors  52 B, the first gate conductors  53 A and the second gate conductors  53 B. Of these conductors, the first detection conductors  52 A and the second detection conductor  52 B have the same configurations as those in the semiconductor device A 12  described before, so that the description is omitted. 
     As shown in  FIG. 23 , as viewed along the thickness direction z, each of the first gate conductors  53 A is in the form of a strip elongated in the first direction x. The width B 2   a  of the first gate conductors  53 A is smaller than the width Ba of the first leads  51 A. Each first gate conductor  53 A is made of a metal piece. As shown in  FIG. 24 , the end of each first gate conductor  53 A on the first side in the first direction x is connected to the second electrode  42  of a respective first semiconductor element  40 A with a second bonding layer  49 . The end of each first gate conductor  53 A on the second side in the first direction x is connected to the first gate wiring layer  22 A with a first bonding layer  29 . 
     As shown in  FIG. 24 , each of the first gate conductors  53 A has a has a first layer  533  and a pair of second layers  534 . The first layer  533  is made of an alloy containing iron and nickel. Examples of the alloy are the same as those for the first layer  521 A of the pillow part  521  of the first detection conductor  52 A. The paired second layers  534  are made of a metal. Examples of the metal are the same as those for the paired second layers  521 B of the pillow part  521  of the first detection conductor  52 A. The first layer  533  is sandwiched between the paired second layers  534  in the thickness direction z. In this way, the first gate conductor  53 A is a laminate of a plurality of metal layers in the thickness direction z. The ratio of the thickness t 5   a  of the first layer  533  at the end on the first side in the first direction x and the thickness t 6   a  of the first layer  533  at the end on the second side in the first direction x may be t 5   a :t 6   a= 1:2, for example. The coefficient of linear expansion of the first gate conductor  53 A having such a configuration is in a range of 0 to 8×10 −6 /° C. In contrast, the coefficient of linear expansion of the first conductive layer  20 A is about 16×10 −6 /° C. Thus, the coefficient of linear expansion of the first gate conductors  53 A is smaller than that of the first conductive layer  20 A. The first layer  533  of the first gate conductor  53 A has a transitional surface  533 A. The transitional surface  533 A is a curved surface located at the section where the thickness of the first layer  533  changes from the thickness t 5   a  to the thickness t 6   a.    
     As shown in  FIG. 25 , as viewed along the thickness direction z, each of the second gate conductors  533  is in the form of a strip elongated in the first direction x. The width  32   b  of the second gate conductors  533  is smaller than the width Bb of the second leads  51 B. Each second gate conductor  53 B is made of a metal piece. As shown in  FIG. 26 , the end of each second gate conductor  53 B on the first side in the first direction x is connected to the second gate wiring layer  22 B with a first bonding layer  29 . The end of each second gate conductor  53 B on the second side in the first direction x is connected to the second electrode  42  of a respective second semiconductor element  403  with a second bonding layer  49 . 
     As shown in  FIG. 26 , each of the second gate conductors  533  has a first layer  533  and a pair of second layers  534 . The ratio of the thickness t 5   b  of the first layer  533  at the end on the first side in the first direction x and the thickness t 6   b  of the first layer  533  at the end on the second side in the first direction x may be t 5   b :t 6   b= 2:1, for example. Other configurations of the first layer  533  and the second layers  534  of each second gate conductor  53 B are the same as those of the first layer  533  and the second layers  534  of each first gate conductor  53 A, so that the description of such configurations is omitted. Note that the coefficient of linear expansion of the second conductive layer  20 B is generally equal to that of the first conductive layer  20 A. Thus, the coefficient of linear expansion of the second gate conductor  53 B is smaller than that of the second conductive layer  20 B. The first layer  533  of the second gate conductor  53 B has a transitional surface  533 A. The transitional surface  533 A is a curved surface located at the section where the thickness of the first layer  533  changes from the thickness t 5   b  to the thickness t 6   b.    
     The advantages of the semiconductor device A 10  are described below. 
     The semiconductor device A 10  includes the first semiconductor elements  40 A each having a first electrode  41  and a second electrode  42  and bonded for electrical connection to the first conductive layer  20 A, the first leads  51 A connected to the first electrodes  41  and the second conductive layer  20 B, the first detection conductors  52 A, and the second detection conductors  52 B. The first detection conductors  52 A are connected to the first electrodes  41 . The first gate conductors  53 A are connected to the second electrodes  42 . In at least either of the first detection conductors  52 A and the first gate conductors  53 A, the ends connected to the first semiconductor elements  40 A have a coefficient of linear expansion smaller than that of the first conductive layer  20 A. Such an arrangement reduces at least either of the thermal stress generated between the first electrodes  41  and the first detection conductors  52 A and the thermal stress generated between the second electrodes and the first gate conductors  53 A. As a result, the possibility of detachment from the first semiconductor elements  40 A is reduced in at least either of the first detection conductors  52 A and the first gate conductors  53 A, which assures the reliability of the semiconductor device A 10 . 
     In the semiconductor device A 10 , the first detection conductors  52 A and the first gate conductors  53 A have pillow parts  521 ,  531  connected to the first semiconductor elements  40 A and wire parts  522 ,  532  connected to the pillow parts  521 ,  531 . The coefficient of linear expansion of the pillow parts  521 ,  531  is smaller than that of the first conductive layer  20 A. With such an arrangement, the first detection conductors  52 A and the first gate conductors  53 A have, at their ends connected to the first semiconductor elements  40 A, a coefficient of linear expansion smaller than the first conductive layer  20 A. 
     Each pillow part  521 ,  531  has a first layer  521 A,  531 A made of an alloy containing iron and nickel and a pair of second layers  521 B,  531 B made of a metal different from the first layer  521 A,  531 A. The first layer  521 A,  531 A is sandwiched between the paired second layers  521 B,  531 B in the thickness direction z. With such an arrangement, the coefficient of linear expansion of the pillow parts  521 ,  531  can be made smaller than that of the first conductive layer  20 A. Also, such an arrangement allows for reliable connection of the pillow parts  521 ,  531  to both of the first semiconductor elements  40 A and the wire parts  522 ,  532 . 
     The first layers  521 A,  531 A of the pillow parts  521 ,  531  can be made of a semiconductor material, instead of an alloy containing iron and nickel. In such a case, the coefficient of linear expansion of the pillow parts  521 ,  531  becomes closer to that of the first semiconductor element  40 A. This allows for more effective reduction of at least either of the thermal stress generated between the first electrodes  41  and the first detection conductors  52 A and the thermal stress generated between the second electrodes  42  and the first gate conductors  53 A. 
     In the semiconductor device A 11 , the first layer  521 A,  531 A of each pillow part  521 ,  531  has a lower layer portion  521 C,  531 C and an upper layer portion  521 D,  531 D. As viewed along the thickness direction z, the area of the upper layer portion  521 D,  531 D is larger than that of the lower layer portion  521 C,  531 C. With such an arrangement, the pillow part  521 ,  531  has a relatively large area for connecting the wire part  522 ,  532 , which makes easier the connection of the wire part  522 ,  532  to the pillow part  521 ,  531 . 
     In the semiconductor device A 12 , each first detection conductor  52 A is made of a metal piece. The coefficient of linear expansion of the first detection conductors  52 A is smaller than that of the first conductive layer  20 A. With such an arrangement, the first detection conductors  52 A have, at their ends connected to the first semiconductor elements  40 A, a coefficient of linear expansion smaller than the first conductive layer  20 A. 
     Each of the first detection conductors  52 A of the semiconductor device A 12  has a first layer  523  made of an alloy containing iron and nickel and a pair of second layers  524  made of a metal different from the first layer  523 . The first layer  523  is sandwiched between the paired second layers  524  in the thickness direction z. With such an arrangement, the coefficient of linear expansion of the first detection conductors  52 A can be made smaller than that of the first conductive layer  20 A. Also, such an arrangement allows for reliable connection of the first detection conductors  52 A to both of the first semiconductor elements  40 A and the first detection wiring layer  21 A. 
     In the semiconductor device A 10 , the first detection wiring layer  21 A and the first gate wiring layer  22 A are formed on the front surface  101  of the insulating support member  10 . Such an insulating support member  10 , formed with the first conductive layer  20 A, the first detection wiring layer  21 A and the first gate wiring layer  22 A on the front surface  101 , can be easily made by using a DBC (trademark) substrate. 
     The semiconductor device A 10  further includes the second semiconductor elements  40 B each having a first electrode  41  and a second electrode  42  and bonded for electrical connection to the second conductive layer  20 B, the second leads  51 B connected to the first electrodes  41  of the second semiconductor elements  40 B, the second detection conductors  52 B and the second gate conductors  53 B. The second detection conductors  52 B are connected to the first electrodes  41  of the second semiconductor elements  40 B. The second gate conductors  53 B are connected to the second electrodes  42  of the second semiconductor elements  40 B. In at least either of the second detection conductors  52 B and the second gate conductors  53 B, the ends connected to the second semiconductor elements  40 B have a coefficient of linear expansion smaller than that of the second conductive layer  20 B. Such an arrangement reduces at least either of the thermal stress generated between the first electrodes  41  of the second semiconductor elements  40 B and the second detection conductor  52 B and the thermal stress generated between the second electrodes  42  of the second semiconductor elements  40 B and the second gate conductors  53 B. As a result, the possibility of detachment from the second semiconductor elements  40 B is reduced in at least either of the second detection conductors  52 B and the second gate conductors  533 . 
     The semiconductor device A 10  further includes the first input terminal  31  and the second input terminal  32 . The first input terminal  31  is electrically connected to the first conductive layer  20 A. The second input terminal  32  is electrically connected to the second leads  51 B. The second leads  51 B are connected to the second input terminal  32 . Thus, the second input terminal  32  and the second leads  51 B can be formed as an integral part, which reduces the number of parts of the semiconductor device A 10 . 
     The first input terminal  31  and the second input terminal  32  are located on the first side in the first direction x. The first input terminal  31  and the second input terminal  32  are spaced apart from each other in the thickness direction z. As viewed along the thickness direction z, part of the second input terminal  32  (the second terminal part  322 ) overlaps with the first input terminal  31 . With such an arrangement, during the use of the semiconductor device A 10 , the magnetic field generated from the second input terminal  32  reduces the inductance of the first input terminal  31 . 
     Second Embodiment 
     A semiconductor device A 20  according to a second embodiment is described below based on  FIGS. 27-32 . In these figures, the elements that are identical or similar to those of the semiconductor device A 10  are denoted by the same reference signs as those used for the semiconductor device A 10  and are not described. In  FIG. 27 , the sealing resin  60  is illustrated as transparent for the convenience of understanding. Thus, the sealing resin  60  are indicated by imaginary lines (two-dot chain lines). 
     The semiconductor device A 20  differs from the semiconductor device A 10  in that the semiconductor device A 20  is provided with a pair of insulating layers  23  and does not include a metal substrate  69 . The semiconductor device A 20  differs from the semiconductor device A 10  also in configurations of the first detection wiring layer  21 A, the second detection wiring layer  21 B, the first gate wiring layer  22 A, the second gate wiring layer  22 B, the first semiconductor elements  40 A, the second semiconductor elements  40 B, the first leads  51 A and the second leads  51 B. 
     As shown in  FIGS. 27, 29 and 30 , the paired insulating layers  23  are arranged on the first conductive layer  20 A and the second conductive layer  20 B. The insulating layers  23  are spaced apart from each other in the first direction x. Each of the insulating layers  23  is in the form of a strip elongated in the second direction y. The insulating layer  23  that is offset toward the first side in the first direction x is on the first conductive layer  20 A. The insulating layer  23  that is offset toward the second side in the first direction x is on the second conductive layer  20 B. The insulating layers  23  may be made of glass epoxy resin, for example. 
     As shown in  FIGS. 27, 29 and 30 , the first detection wiring layer  21 A and the first gate wiring layer  22 A are arranged on one of the insulating layers  23  that is on the first conductive layer  20 A. The second detection wiring layer  21 B and the second gate wiring layer  22 B are arranged on the other one of the insulating layers  23  that is on the second conductive layer  20 B. Thus, in the semiconductor device A 20  again, as viewed along the thickness direction z, the first detection wiring layer  21 A, the second detection wiring layer  21 B, the first gate wiring layer  22 A and the second gate wiring layer  22 B overlap with the front surface  101  of the insulating support member  10 . 
     As shown in  FIGS. 27 and 29 , the first semiconductor elements  40 A are offset toward the second side in the first direction x from the one of the insulating layers  23  that is on the first conductive layer  20 A. In each of the first semiconductor elements  40 A, the second electrode  42  is offset toward the first side in the first direction x. 
     As shown in  FIGS. 27 and 30 , the second semiconductor elements  40 B are offset toward the first side in the first direction x from the other one of the insulating layers  23  that is on the second conductive layer  20 B. In each of the second semiconductor elements  40 B, the second electrode  42  is offset toward the second side in the first direction x. 
     As shown in  FIG. 27 , the dimension of each first lead  51 A in the first direction x is smaller than that in the semiconductor device A 10 . Also, the dimension of each second lead  51 B in the first direction x is smaller than that in the semiconductor device A 10 . 
     As shown in  FIGS. 27 and 28 , a pair of detection terminals  34  takes the place of the pair of gate terminals  35  of the semiconductor device A 10 . Also, a pair of gate terminals  35  takes the place of the pair of detection terminal  34  of the semiconductor device A 10 . As shown in  FIG. 28 , the back surface  102  of the insulating support member  10  is exposed from the bottom surface  62  of the sealing resin  60 . 
     As shown in  FIG. 31 , as viewed along the thickness direction z, the first detection conductors  52 A and the first gate conductors  53 A extend from the first semiconductor elements  40 A toward the first side in the first direction x. As shown in  FIG. 32 , as viewed along the thickness direction z, the second detection conductors  52 B and the second gate conductors  538  extend from the second semiconductor elements  40 B toward the second side in the first direction x. Other configurations of each of the first detection conductors  52 A, the second detection conductors  52 B, the first gate conductors  53 A and the second gate conductors  53 B are the same as those in the semiconductor device A 10 , so that the description of such configurations is omitted. 
     First Variation of the Second Embodiment 
     A semiconductor device A 21 , which is the first variation of the semiconductor device A 20 , is described below based on  FIGS. 33 and 34 . The semiconductor device A 21  differs from the semiconductor device A 20  in configuration of the first detection conductors  52 A and the second detection conductors  52 B. 
     As shown in  FIG. 33 , as viewed along the thickness direction z, each of the first detection conductors  52 A is in the form of a strip extending from the first semiconductor element  40 A toward the first side in the first direction x. The width B 1   a  of the first detection conductors  52 A is smaller than the width Ba of the first leads  51 A. Each first detection conductors  52 A is made of a metal piece. Other configurations of the first detection conductors  52 A are the same as those of the first detection conductors  52 A of the semiconductor device A 12 , so that the description is omitted. 
     As shown in  FIG. 34 , as viewed along the thickness direction z, each of the second detection conductors  52 B is in the form of a strip extending from the second semiconductor element  408  toward the second side in the first direction x. The width B 1   b  of the second detection conductors  52 B is smaller than the width Bb of the second leads  518 . Each second detection conductor  528  is made of a metal piece. Other configurations of the second detection conductors  52 B are the same as those of the second detection conductors  52 B of the semiconductor device A 12 , so that the description is omitted. 
     Second Variation of the Second Embodiment 
     A semiconductor device A 22 , which is the second variation of the semiconductor device A 20 , is described below based on  FIGS. 35 and 36 . The semiconductor device A 22  differs from the semiconductor device A 20  in configuration of the first detection conductors  52 A, the second detection conductors  52 B, the first gate conductors  53 A and the second gate conductors  533 . Of these conductors, the first detection conductors  52 A and the second detection conductors  52 B have the same configurations as those of the semiconductor device A 21 , so that the description is omitted. 
     As shown in  FIG. 35 , as viewed along the thickness direction z, each of the first gate conductors  53 A is in the form of a strip extending from the first semiconductor element  40 A toward the first side in the first direction x. The width Eta of the first gate conductors  53 A is smaller than the width Ba of the first leads  51 A. The length L 2   a  of the first gate conductors  53 A is smaller than the length L 1   a  of the first detection conductors  52 A. Each first gate conductor  53 A is made of a metal piece. Other configurations of the first gate conductors  53 A are the same as those of the first gate conductors  53 A of the semiconductor device A 13 , the description is omitted. 
     As shown in  FIG. 36 , as viewed along the thickness direction z, each of the second gate conductors  53 B is in the form of a strip extending from the second semiconductor element  40 B toward the second side in the first direction x. The width  32   b  of the second gate conductors  53 B is smaller than the width Bb of the second leads  51 B. The length L 2   b  of the second gate conductors  533  is smaller than the length Lib of the second detection conductors  52 B. Each second gate conductor  53 B is made of a metal piece. Other configurations of the second gate conductors  533  are the same as those of the second gate conductors  53 B of the semiconductor device A 13 , so that the description is omitted. 
     The advantages of the semiconductor device A 20  are described below. 
     As with the semiconductor device A 10 , the semiconductor device A 20  includes the first semiconductor elements  40 A each having a first electrode  41  and a second electrode  42  and bonded for electrical connection to the first conductive layer  20 A, the first leads  51 A connected to the first electrodes  41  and the second conductive layer  20 B, the first detection conductors  52 A, and the second detection conductors  52 B. The first detection conductors  52 A are connected to the first electrodes  41 . The first gate conductors  53 A are connected to the second electrodes  42 . In at least either of the first detection conductors  52 A and the first gate conductors  53 A, the ends connected to the first semiconductor elements  40 A have a coefficient of linear expansion smaller than that of the first conductive layer  20 A, which assures the reliability of the semiconductor device A 20 . 
     The semiconductor device A 20  is provided with an insulating layer  23  on the first conductive layer  20 A. The first detection wiring layer  21 A and the first gate wiring layer  22 A are arranged on the insulating layer  23 . Such an arrangement makes it possible to increase the area of the first conductive layer  20 A as viewed along the thickness direction z and thereby to promote heat dissipation from the semiconductor device A 20 . Moreover, by arranging the first semiconductor elements  40 A offset from the insulating layer  23  toward the second side in the first direction x, the dimension of each first lead  51 A in the first direction x can be reduced. As a result, the parasitic resistance of the semiconductor device A 20  can be reduced. 
     The semiconductor device according to the present disclosure is not limited to the foregoing embodiments. The specific configuration of each part of the semiconductor device may be varied in design in many ways.