Patent Publication Number: US-2021193827-A1

Title: Semiconductor Arrangement with an Integrated Temperature Sensor

Description:
TECHNICAL FIELD 
     This disclosure in general relates to a semiconductor arrangement that includes a temperature sensor integrated in a semiconductor body. 
     BACKGROUND 
     In various kinds of semiconductor arrangements, it is desired to measure the temperature inside a semiconductor body. One example of such semiconductor arrangement is a power transistor. A power transistor includes a plurality of transistor cells that are integrated in semiconductor body. A power transistor may be operated in an on-state and an off-state, wherein in the on-state power may be dissipated in the semiconductor body so that the semiconductor body is heated up. A temperature sensor integrated in the semiconductor body is useful to detect an overtemperature so that the power transistor can be switched off in order to protect the power transistor from being damaged or destroyed. 
     There is a need for a space saving integrated temperature sensor, in particular a temperature sensor that may be implemented in a power transistor and can be produced in a cost-efficient way. 
     SUMMARY 
     One example relates to a semiconductor arrangement with a semiconductor body and a temperature sensor integrated in the semiconductor body. The temperature sensor includes a first semiconductor region of a first doping type arranged, in a vertical direction of the semiconductor body, between a second semiconductor region of a second doping type and a third semiconductor region of the second doping type, and a contact plug ohmically connecting the first semiconductor region and the second semiconductor region. The first semiconductor region includes a base region section spaced apart from the contact plug in a first lateral direction of the semiconductor body and a resistor section arranged between the base region section and the contact plug. The resistor section is implemented such that an ohmic resistance of the resistor section between the base region section and the contact plug is at least 1 MΩ. 
     Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Examples are explained below with reference to the drawings. The drawings serve to illustrate certain principles, so that only aspects necessary for understanding these principles are illustrated. The drawings are not to scale. In the drawings the same reference characters denote like features. 
         FIGS. 1A-1D  show a top view and vertical cross-sectional views, respectively, of a temperature sensor according to one example; 
         FIG. 2  illustrates the function of the temperature sensor according to  FIGS. 1A-1D ; 
         FIG. 3  illustrates a measurement current over a measurement voltage in a temperature sensor according to one example; 
         FIG. 4  illustrates a measurement current over a temperature in a temperature sensor according to one example; 
         FIG. 5  illustrates a modification of the temperature sensor shown in  FIGS. 1A-1D ; 
         FIG. 6  shows a vertical cross-sectional view of one example of a semiconductor arrangement that includes a vertical transistor device with a plurality of transistor cells and a temperature sensor of the type shown in  FIGS. 1A-1D ; 
         FIG. 7  shows a vertical cross-sectional view of a transistor cell according to one example in detail; 
         FIG. 8  shows a top view of the semiconductor arrangement shown  4 ; 
         FIG. 9  shows a vertical cross-sectional view of a transistor cell according to another example in detail; 
         FIG. 10  shows a vertical cross-sectional view of an isolation between the temperature sensor and the transistor device according to one example; 
         FIG. 11  shows a vertical cross-sectional view of the isolation according to another example; and 
         FIG. 12  shows a vertical cross-sectional view of the isolation according to yet another example; 
         FIG. 13  shows a top view of the semiconductor arrangement according to one example; and 
         FIG. 14  shows a top view of the semiconductor arrangement according to another example. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings. The drawings form a part of the description and for the purpose of illustration show examples of how the invention may be used and implemented. It is to be understood that the features of the various embodiments described herein may be combined with each other, unless specifically noted otherwise. 
       FIGS. 1A-1D  illustrate one example of a temperature sensor TES integrated in a semiconductor body  100 , wherein only a section of the semiconductor body  100  in which the temperature sensor TES is integrated is illustrated.  FIG. 1A  illustrates a top view on a first surface  101  of the semiconductor body  100 ,  FIG. 1B  illustrates a vertical cross-sectional view of the semiconductor body  100  in a first vertical section plane B-B,  FIG. 1C  illustrates a vertical cross-sectional view of the semiconductor body  100  in a second vertical section plane C-C, and  FIG. 1D  illustrates a vertical cross-sectional view of the semiconductor body  100  in a third vertical section plane D-D. The first vertical section plane B-B extends in a vertical direction z and a first lateral direction x of the semiconductor body  100 , the second vertical section plane C-C extends in the vertical direction z and a second lateral direction y, and the third vertical section plane D-D extends in the vertical direction z and the second lateral direction y. The second lateral direction y is perpendicular to the first lateral direction x. Further, the second vertical section plane C-C and the third vertical section plane D-D cut through the semiconductor body  100  at different positions in the first lateral direction x. 
     Referring to  FIGS. 1A-1D  the temperature sensor TES includes a first semiconductor region  11  of a first doping type, a second semiconductor region  21  of a second doping type complementary to the first doping type, and a third semiconductor region  30  of the second doping type. The first semiconductor region  11  is arranged between the second semiconductor region  21  and the third semiconductor region  30  in the vertical direction z of the semiconductor body  100 . The temperature sensor TES further includes a contact plug  4  that ohmically connects the first semiconductor region  11  and the second semiconductor region  21 . “To ohmically connect” means that there is no rectifying junction in a current path from the first semiconductor region  11  via the contact plug  4  to the second semiconductor region  21 , or vice versa. Thus, there is an ohmic contact between the contact plug  4  and each of the first semiconductor region  11  and the second semiconductor region  21 . To achieve such ohmic contacts, the contact plug  4  may adjoin each of the first semiconductor region  11  and the second semiconductor region  21 . Optionally, a contact region  11 ′ (illustrated in dashed lines) of the same doping type as the first semiconductor region  11 , but more highly doped than the first semiconductor region  11  is arranged between the contact plug  4  and the first semiconductor region  11 . A doping concentration of the contact region  11 ′ is high enough to achieve an ohmic contact between the contact plug  4  and the contact region  11 ′, so that there is an ohmic connection between the contact plug  4  and the first semiconductor region  11 . Equivalently, a contact region  21 ′ (illustrated in dashed lines) that is of the second doping type and more highly doped than the second semiconductor region  21  may be arranged between the contact plug  4  and the second semiconductor region  21 . A doping concentration on this contact region  21 ′ is high enough to achieve an ohmic connection between the contact region  21 ′ and the second semiconductor region  21 . 
     The contact plug  4  includes a metal or a doped polycrystalline semiconductor material such as doped polysilicon. The metal includes, for example, platinum (Pt), aluminum (Al), copper (Cu), silver (Ag), titanium (Ti), or alloys including two or more of these metals. According to one example, the contact plug includes a layer stack including two or more of these metals and/or alloys. 
     The semiconductor body  100  includes a conventional semiconductor material such as silicon (Si), silicon carbide (SiC), gallium arsenide (GaAs), gallium nitride (GaN), or the like. According to one example, the first doping type is a p-type and the second doping type is a n-type. In a silicon based semiconductor body  100 , for example, the first semiconductor region  11  may include boron (B) atoms as p-type doping atoms, and the second and third semiconductor regions  21 ,  30  may include at least one of phosphorous (P) atoms or arsenic (As) atoms as n-type doping atoms. In a silicon semiconductor body, a doping concentration of the optional contact regions  11 ′,  21 ′ is at least 1E18 cm −3 . 
     In the temperature sensor TES illustrated in  FIGS. 1A-1D , the first semiconductor region  11 , the second semiconductor region  21  and the third semiconductor region  30  form a bipolar transistor. More specifically, a section of the first semiconductor region  11  forms a base region of the bipolar transistor, the second semiconductor region  21  forms an emitter region of the bipolar transistor, and the third semiconductor region  30  forms a collector region of the bipolar transistor. The first, second and third regions  11 ,  21 ,  30  will therefore also be referred to as base, emitter and collector regions in the following. 
     The functionality of the temperature sensor TES and further features of the temperature sensor TES are explained with reference to  FIG. 2 .  FIG. 2  shows the semiconductor body  100  in the first vertical section plane B-B in greater detail. Referring to  FIG. 2 , measuring a temperature of the semiconductor body  100  using the temperature sensor TES includes applying a measurement voltage V CE  between the third semiconductor region (collector region)  30  and the contact plug  4 , which is connected to the first region (base region)  11  and the second region (emitter region)  21 . The contact plug  4  forms an emitter node E of the bipolar transistor, and the collector region  30  forms a collector node C or is connected to a collector node C. 
     A circuit symbol of the bipolar transistor formed by the first, second and third semiconductor regions  11 ,  21 ,  30  is also illustrated in  FIG. 2 . Just for the purpose of illustration it is assumed that the first doping type of the base region  11  is a p-type and the second doping type of the collector and emitter regions  30 ,  21  is an n-type so that the bipolar transistor is an n-p-n bipolar transistor. 
     The measurement voltage V CE  is a DC voltage and, according to one example, is essentially constant. The measurement voltage is provided by a respective voltage source  71 . Any type of DC voltage source can be used to generate the measurement voltage V CE  between the collector node C, which is formed by the third semiconductor region  30 , and the emitter node E. According to one example, the measurement voltage V CE  is less than 5V, less than 2V, or even less than 1V. According to one example, the measurement voltage V CE  is between 0.2V and 0.7V. 
     A rather low measurement voltage selected from between 0.2 V and 0.7 V is beneficial for various reasons. The measurement current I CE  is not only dependent on the temperature, but is also dependent on the measurement voltage V CE , wherein the dependency of the measurement current I CE  on the measurement voltage V CE  increases as the measurement voltage V CE  increases. A high dependency of the measurement current I CE  on the measurement voltage V CE  has the effect that inadvertent variations of the measurement voltage V CE  may cause variations of the measurement current I CE , even if the temperature does not change. In a voltage range of the measurement voltage V CE  of between 0.2V and 0.7V the dependency of the measurement current I CE  on the measurement voltage V CE  is rather low. This is illustrated in  FIG. 3  which shows the measurement current I CE  at a fixed temperature (180° C. in this example) dependent on the measurement voltage V CE . As can be seen, in a range of between 0.1V and 0.4V the measurement current I CE  is widely independent on the measurement voltage V CE , wherein this range can be extrapolated to higher measurement voltages up to 0.7 V. Thus, when selecting the measurement voltage V CE  from a range of between 0.2 V and 0.7 V variations of the measurement voltage V CE  at the same temperature do not significantly affect the measurement current I CE . 
     Further, when applying the measurement voltage V CE  it takes some time for the temperature sensor to operate in a steady mode and, at a given temperature, provide a constant measurement current. The higher the measurement voltage V CE  the longer this takes. Thus, when the measurement voltage V CE  is rather low, such as being selected from between 0.2V and 0.7V, a reliable measurement current I CE  will be provided faster than when using high measurement voltages V CE . 
     The measurement voltage V CE  causes a measurement current I CE  to flow between the collector node C and the emitter node E of the bipolar transistor of the temperature sensor TES. This measurement current I CE  is dependent on the temperature of the semiconductor body  100  in a region in which the temperature sensor TES is integrated, wherein the measurement current I CE  increases as the temperature increases. 
     According to one example, a current sensor  72  is configured to measure the measurement current I CE  and to provide a measurement signal S ICE  that represents the measurement current I CE  and, therefore, the temperature of the semiconductor body  100 . Any type of current sensor  71  may be used to measure the measurement current I CE  and provide the current measurement signal S ICE . Examples of the current sensor  71  include, but are not restricted to, a Hall sensor, an inductive current sensor, a shunt resistor based current sensor, or the like. 
     A control circuit (not illustrated) may receive the measurement signal S ICE  and output a signal that represents the temperature T associated with the measurement current S ICE . The control circuit may be configured to obtain the temperature T based on the measurement current S ICE  by at least one of the following: calculating the temperature T based on the measurement current S ICE  using a predefined formula that reflects the relationship between the measurement current S ICE  output by the temperature sensor TES and the associated temperature; obtaining a temperature value from a lookup table that includes a plurality of value pairs each including a measurement signal S ICE  value and an associated temperature value. 
     As the contact plug  4  is ohmically connected to the base region  11 , applying the measurement voltage V CE  between the emitter node E and the collector node C is equivalent to applying the measurement voltage V CE  across a p-n junction between the base region  11  and the collector region  30 , wherein a polarity of the measurement voltage V CE  is such that this p-n junction is reverse biased. Reverse biasing the p-n junction between the base region  11  and the collector region  30  causes a leakage current Ica to flow via the p-n junction from the collector region  30  to the base region  11 . Charge carriers that cross the p-n junction from the collector region  30  to the base region  11  at positions spaced apart from the contact plug  4  in the first lateral direction x flow in the base region  11  in the lateral direction x towards the contact plug  4 . 
     According to one example, a doping concentration of the emitter region  21  is much higher than a doping concentration of the base region  11  so that the electrical potential of the emitter region  21  can be considered to be essentially the same at each position of the emitter region  21  in the first lateral direction x, wherein this electrical potential equals the electrical potential of the contact plug  4 . According to one example, a doping concentration of the emitter region  21  is between 1E18 cm −3  and 1E21 cm −3 , for example. 
     In the first semiconductor region  11 , however, the leakage current flowing in the lateral direction x causes a voltage drop such that in the first semiconductor region  11 , the electrical potential increases as a distance to the contact plug  4  increases. The first semiconductor region  11  can be considered to include a base region section  11   1  and a resistor section  11   2 . The base region section  11   1  is a section of the first semiconductor region  11  that is spaced apart from the contact plug  4  in the first lateral direction x and forms a base region of the bipolar transistor. The resistor section  11   2  is a section of the first semiconductor region  11  that is arranged between the base region section  11   1  and the contact plug  4 . This resistor section  11   2  forms an ohmic resistance R for charge carriers entering the base region section  11   1  via the reverse biased p-n junction and flowing in the first lateral direction x from the base region section  11   1  via the resistor section to the contact plug  4 . 
     An ohmic resistance of the resistor section  11   2  between the base region section  11   1  and the contact plug  4  is at least 1 MΩ. According to one example, the ohmic resistance is between 1 MΩ and 15 MΩ. According to one example, the ohmic resistance is higher than 3 MΩ or higher than 5 MΩ. 
     A resistor section of this type has the effect that even a small leakage current I CB  from the collector region  30  to the base region section  11   2  via the p-n junction causes a voltage drop V BE  along the resistor section  11   2  that is high enough to switch on the bipolar transistor, so that the measurement current I CE  is significantly higher than the leakage current I CB . 
     The measurement current I CE  of this kind of temperature sensor TES is exponentially dependent on the temperature T and increases as the temperature increases.  FIG. 4  illustrates, on a logarithmic scale, the measurement current I CE  of a temperature sensor according to one example dependent on the temperature T over a temperature range of between 25° C. and 175° C. In addition to the measurement current I CE , the lower leakage current I CB  is also illustrated in this example. An amplification factor α, which is the ratio between the leakage current I CB  and the measurement current I CE  can be adjusted by suitably selecting the parameters explained above, such as doping concentration of the base region  11 , or the resistance of the resistor section  11   2 . In the example illustrated in  FIG. 4 , this amplification factor (α=I CE /I CB ) is about 2. 
     The curve illustrated in  FIG. 4  shows the measurement current dependent on the temperature of a temperature sensor TES operated with a measurement voltage V CE  of 0.4V, an Arsenic (As) doping concentration of the emitter region  12  of about 1E20 cm −3 , a boron (B) doping concentration of the base region  11  of about 1E17 cm −3 , and a resistance R of the resistance section  11   2  of about 4 MΩ. These specific parameters, however, are only examples. These parameters may be varied in order to achieve a desired relationship between the measurement current I CE  and the temperature T. 
     An exact relationship between the measurement current and the temperature is dependent on various parameters such as, for example, doping concentrations and dimensions of the first, second, and third semiconductor regions  11 ,  21 ,  30  and can either be calculated or obtained by measurements or simulations. In each case, however, the measurement current I CE  increases as the temperature increases. 
     The ohmic resistance R of the base region section  11   2  can be adjusted by suitably adjusting the following parameters of the resistor section  11   2 : a cross-sectional area A 1  in a section plane perpendicular to the first lateral direction x, a length d 1  in the first lateral direction x; and a doping concentration. According to one example, the doping concentration is essentially the same in the base region section  11   1  and the resistor section  11   2  and the base region section  11   1  and the resistor section  11   2  have the same cross-sectional area A 1 . 
     The cross-sectional area A 1  of the resistor section  11   2  is the area of the resistor section  11   2  in a section plane extending in the second lateral direction y and the vertical direction z. A dimension w 1  (see  FIGS. 1C and 1D ) of the first semiconductor region  11  and the resistor section  11   2  is referred to as width w 1  in the following, Further, a dimension h 1  of the first semiconductor region  11  and the resistor section  11   2  in the vertical direction z is referred to as height in the following. The cross-sectional area A 1  is given by the width w 1  multiplied with the height h 1 , 
         A 1= w 1· h 1  (1).
 
     According to one example, the cross-sectional area A 1  is selected from between 3 square micrometres (μm 2 ) and 15 square micrometres. According to one example, the doping concentration of the first semiconductor region  11  is selected from between 1E16 cm −3  and 1E18 cm −3 . According to one example, the first semiconductor region  11  is a boron (B) doped p-type layer. In this case, a doping concentration of between 1E16 cm −3  and 1E18 cm −3  is equivalent to a specific resistance of between 1.464 Ω·cm and 0.048 Ω·cm. A doping concentration of 1E17 cm −3 , for example, corresponds to a specific resistance of about 0.206 Ω·cm. 
     According to one example, the doping concentration of the first semiconductor region  11  and the cross-sectional area A 1  are adapted to one another such that a specific lateral resistance of the resistor section  11   2  is between 3 kΩ/μm and 100 kΩ/μm. The specific lateral resistance is given by the cross-sectional area A 1  multiplied with the respective specific resistance given by the doping concentration. The resistance R is then given by the specific lateral resistance multiplied with the length. A resistance R of the resistor region  11   2  of 1 MΩ, for example, may be achieved by adjusting the specific lateral resistance such that is essentially equals 3 kΩ/μm and by making the resistor section  11   2  longer than 333 micrometers (μm). A specific lateral resistance of 3 kΩ/μm can be achieved, for example, by adjusting the specific resistance (by suitably doping) to 1.2 Ω·cm and adjusting the cross-sectional area to 4 square micrometers (1.2 Ω·cm/4 μm 2 =3 kΩ/μm). 
     It should be noted that the base region section  11   1  is not necessarily distinguishable from the resistor section  11   2  with regard to doping concentration, cross-sectional area, or specific lateral resistance. In the first semiconductor region  11 , the base region section  11   1  is a section that is spaced apart from the contact plug  4  by the resistor section  11   2  (which is another section of the first region  11 ), wherein, as explained above, an ohmic resistance R of the resistor section  11   2  between the base region section  11   1  and the contact plug  4  is at least 1 MΩ. Referring to the above, the ohmic resistance R, at a given specific lateral resistance of the resistor section  11   2 , is associated with a certain length d 1 . An overall length of the resistor section  11   2  and the base region  11   1  section is therefore greater than d 1 . According to one example, a length of the base region section  11   1  in the first lateral direction x is between 0.1 times and 2 times d 1 , in particular between 0.1 times and 0.5 times d 1 , so that the overall length of the resistor section  11   2  and the base region section  11   1  is between 1.1 times and 3 times d 1 , in in particular between 1.1 times and 1.5 times d 1  in this example. Consequently, an overall resistance of the base region  11  in the base region section  11   1  and the resistor section  11   2  is between 1.1 times and 3 times the desired ohmic resistance R of the resistor section  11   2 , in particular between 1.1 times and 1.5 times the desired ohmic resistance R of the resistor section  11   2 . Referring to the above, the desired ohmic resistance R of the resistor section  11   2  is between 1 MΩ and 15 MΩ, for example. 
     According to one example, the overall resistance of the base region  11  in the base region section  11   1  and the resistor section  11   2  is higher than 1.1 MΩ(=1.1×1 MΩ) higher than 3.3 MΩ(=1.1×3 MΩ), higher than 5.5 MΩ(=1.1×5 MΩ), or higher than 16.5 MΩ(=1.1×15 MΩ). 
       FIG. 5  shows a vertical cross-sectional view of a temperature sensor TES according to another example. In this example, the temperature sensor TES includes two contact plugs  4   1 ,  4   2  that are each ohmically connected to the first semiconductor region  11  and the second semiconductor region  21  and that are spaced apart from each other in the first lateral direction x. In this example, the temperature sensor TES includes a base region section  11   2  between the two contact plugs  4   1 ,  4   2  and two resistor sections, a first resistor section  11   11  arranged between a first one 4 1  of the contact plugs  4   1 ,  4   2  and the base region section  11   2 , and a second resistor section  11   12  arranged between a second one 4 2  of the contact plugs  4   1 ,  4   2  and the base region section  11   2 . Everything explained with reference to  FIG. 2  regarding a resistance, a doping concentration, and dimensions of the base region section  11   2  and the resistor section  11   1  applies to the base region section  11   2  and the resistor sections  11   11 ,  11   12  illustrated in  FIG. 5  accordingly. 
     According to one example, the temperature sensor TES is used to measure the temperature in a transistor device. In this example, the temperature sensor TES is integrated in the same semiconductor body  100  as the transistor device. A vertical cross-sectional view of a semiconductor body  100  in which the temperature sensor TES and a transistor device are integrated is illustrated in  FIG. 6 . In this example, the transistor device is a vertical transistor device, more specifically, a vertical power MOSFET and includes a plurality of transistor cells TC. One example of such transistor cell TC is illustrated in  FIG. 7  in greater detail. 
     Referring to  FIGS. 4 and 5 , each transistor cell TC includes a body region  12  of the first doping type, a source region  22  of the second doping type, and a drift region  32  of the second doping type, wherein the body region  12  is arranged between the source region  22  and the drift region  32  in the vertical direction z of the semiconductor body  100 . The transistor cell TC further includes a gate structure  6 , wherein the gate structure includes an electrode  61  that is arranged adjacent the body region  12  and is dielectrically insulated from the body region  12  by a gate dielectric  61 . In the example shown in  FIGS. 4 and 5 , the gate electrode  61  is arranged in a trench that extends from the first surface  101  into the semiconductor body. This, however, is only an example. According to another example (not shown) the gate electrode  61  is a planar gate electrode that is arranged on top of the first surface  101 . 
     Referring to  FIG. 7 , each of the body region  12  and the source region  22  is connected to a source node S of the transistor device. For this, the body region  12  and the source region  22  may be connected to a source plug  7  that extends into the semiconductor body  100 , wherein the source plug  7  is connected to a source node S. According to one example, the source plug  7  is ohmically connected to the source region  22  and the body region  12 . For this, an optional contact region of the first doping type and more highly doped than the body region  12  may be arranged between the body region  12  and the source plug  7  in order to achieve an ohmic contact between the source plug  7  and the body region  12 . Equivalently, a contact region of the second doping type and more highly doped than the source region  22  may be arranged between the source region  22  and the contact plug  7  in order to achieve an ohmic contact between the source plug  7  and the source region  22 . Such contact regions, however, are not illustrated in  FIGS. 4 and 5 . The source node S may be formed by a source metallization (not shown) that is formed on top of the first surface  101  and is connected to the source plugs  7 . 
     Connecting the body region  12  and the source region  22  to the source node S via a contact plug  7  extending into the semiconductor body  100  is only an example. According to another example (not shown) a section of the body region  12  extends to the first surface  101  and the body region  12  and the source region  22  are connected to a source metallization formed on top of the first surface  101 , wherein the source metallization forms the source node S or is connected to the source node S. 
     Referring to  FIGS. 4 and 5 , each transistor cell TC further includes a drain region  34  that is separated from the body region  12  by the drift region  32  and adjoins a second surface  102  opposite the first surface  101  of the semiconductor body  100 . The drain region  34  is of the same doping type as the drift region  32 , but has a higher doping concentration. A doping concentration of the drift region  32  is selected from between 1E13 cm −3  and 1E17 cm −3 , for example, and doping concentration of the drain region  34  is selected from between 1E19 cm −3  and 1E21 cm −3 , for example. 
     The drain region  34  may adjoin the drift region  32 . According to another example (not illustrated) a buffer region of the first doping type is arranged between the drift region  32  and the drain region  34 . 
     The transistor cells TC of the transistor device are connected in parallel in that the gate electrodes  61  of the individual transistor cells TC are connected to a common gate node G, the source and body regions  22 ,  12  of the transistor cells TC are connected to the common source node S, and the drain regions  34  of the transistor cells TC are connected to a common drain node D. The drift regions  32  of the individual transistor cells TC may be formed by one common semiconductor layer. Equivalently, the drain regions  34  of the transistor cells TC may be formed by one common semiconductor layer. The third semiconductor region  30  of the temperature sensor TES may be formed by a section of the semiconductor layer that forms the drift regions  32  and by a section of the semiconductor layer that forms the drain regions  34 . In this case, the third semiconductor region  30  includes two partial regions, a first partial region  31  that has the same doping concentration as the drift regions  32  of the transistor cells TC, and a second partial region  33  that has the same doping concentration as the drain regions  34  of the transistor cells TC. The collector C of the temperature sensor TES is formed by the second partial region  33  in this example. 
     The first semiconductor region  11  of the temperature sensor TES may have the same doping concentration or doping profile as the body regions  12  of the transistor cells TC. In this case, the first semiconductor region  11  of the temperature sensor TES and the body regions  12  of the transistor cells TC may be formed by the same manufacturing process. Equivalently, the second semiconductor region  21  of the temperature sensor TES may have the same doping concentration or doping profile as the source regions  22  of the transistor cells TC. In this case, the second semiconductor region  21  of the temperature sensor TES and the source regions  22  of the transistor cells TC may be formed by the same manufacturing process. The “doping profile” is given by the doping concentration of the respective region  21 ,  22  at a respective position. 
       FIG. 8  shows a top view of the arrangement shown in  FIG. 6 . In this example, the transistor cells TC are stripe cells (elongated transistor cells). That is, the transistor cells TC are elongated in the second lateral direction y. The contact plugs  7  may be elongated contact plugs, as illustrated in the case of one of the transistor cells TC shown in  FIG. 8 . Optionally, a plurality of contact plugs  7  may be arranged spaced apart from each other in the second lateral direction y as illustrated in the case of another transistor cell TC shown in  FIG. 8 . The temperature sensor TES may be implemented as explained with reference to  FIGS. 1A-1D and 2  or as explained with reference to  FIG. 5 . 
       FIG. 9  shows a modification of the transistor cell TC shown in  FIG. 7 . In this example, the transistor cell TC further includes a field electrode  63  that is dielectrically insulated from the drift region  32  by a field electrode dielectric  64 . The field electrode  63  may be connected to the source node S (as illustrated) or may be connected to the gate node G (not illustrated). The gate electrode  61  is dielectrically insulated from the field electrode  63 . 
     Referring to  FIG. 6 , the first and second semiconductor regions  11 ,  21  of the temperature sensor TES are separated from source and body regions  22 ,  12  of the transistor cells TC by an isolation region  5 . This isolation region  5  is configured to absorb a voltage that may occur between the source node S of the transistor device and the emitter node E of the temperature sensor TES when the transistor device and the temperature sensor TES are in operation. This is explained in the following. 
     The transistor device may be used as an electronic switch that switches on or off dependant on a voltage applied between the gate node G and the source node S. In the off-state of the transistor device a voltage between the source node S and the drain node D may reach a voltage level of several ten volts, or even several hundred volts, wherein this voltage is dependent on a voltage blocking capability transistor device. The “voltage blocking capability of the transistor device” is the maximum voltage the transistor device can withstand between the drain node D and the source node S. 
     Referring to  FIG. 2 , a constant voltage is applied between the collector node C of the temperature sensor TES and the emitter node E. The collector node C equals the drain node D of the transistor device so that a voltage V SE  between the source node S and the emitter node E is given by the drain-source voltage V DS  of the transistor device minus the voltage V CE  between the collector node C and the emitter node E of the temperature sensor TES. Referring to the above, the measurement voltage V CE  of the transistor device may be less than 5V and the voltage between the drain node D and the source node S of the transistor device may be several ten volts or several hundred volts, so that the voltage between the source node S and the emitter node E essentially equals the load path voltage V DS  of the transistor device. The isolation region  5  is configured to withstand this voltage. Examples for implementing the isolation region  5  are explained herein further below. 
       FIG. 10  illustrates one example of the isolation region  5  and an adjoining section of the temperature sensor TES. In this example, the isolation region  5  includes a trench that extends from the first surface  101  into the semiconductor body  100  and adjoins the first and second semiconductor regions  21 ,  11  of the temperature sensor TES. The trench of the isolation region  5  extends into the semiconductor layer forming the drift region  32  of the transistor cells (not shown in  FIG. 10 ) and the first partial region  31  of the collector region  30  of the temperature sensor TES. This trench includes an electrically insulating material. This material may be a solid such as an oxide, a nitride, or the like. Alternatively, the trench is at least partially filled with a gas such as air, a noble gas, or the like. 
     Another example of the isolation region  5  is illustrated in  FIG. 11 . In this example, the isolation region includes a trench that is spaced apart from the first and second regions  11 ,  21  of the temperature sensor TES in the first lateral direction x. Further, this trench includes an electrode  52  that is dielectrically insulated from the semiconductor body  100  by an insulator. The insulator  51  is an oxide or a nitride, for example. The electrode  52  may be connected to the source node S. Referring to  FIG. 11 , the isolation region  5  further include a doped region  53  of the first doping type arranged between the trench and the first and second regions  11 ,  21  of the temperature sensor TES. This doped region  53  may have the same doping concentration as the first region  11  of the temperature sensor TES, for example. 
       FIG. 12  illustrates a modification of the isolation region  5  shown in  FIG. 12 . In this example, the isolation region  5  includes two trenches, a first trench with a first electrode  52   1  and a first dielectric  51   1  that is spaced apart from the temperature sensor TES. The electrode  52   1  is connected to the source node S. This trench is equivalent to the trench illustrated in  FIG. 11 . 
     Referring to  FIG. 12 , the isolation region  5  further includes a second trench with a second electrode  52   2  that is dielectrically insulated from the semiconductor body  100  by a second dielectric  51   2 . This second trench adjoins the first and second regions  11 ,  21  of the temperature sensor TES. The electrode  52   2  is connected to the emitter node E, for example. Referring to  FIG. 12 , a section of the semiconductor layer forming the drift region  32  of the transistor cells TC and the first partial region  31  of the collector region  30  of the temperature sensor TES may extend to the first surface  101  of the semiconductor body  100  between the two trenches. 
       FIG. 13  schematically illustrates a top view of an arrangement with the temperature sensor TES and the transistor device. The arrangement with the transistor cells TC is referred to as transistor cell array in the following. In the example shown in  FIG. 13 , the temperature sensor TES is arranged in a corner of the transistor cell array and separated from the transistor cells TC of the cell array by the isolation region  5 . 
     According to another example shown in  FIG. 14 , the temperature sensor TES is surrounded by the transistor cells TC of the cell array and separated from the transistor cells TC by the isolation region  5 . 
     Referring to the above, a control circuit (not illustrated) may receive the current measurement signal S ICE  provided by the temperature sensor TES. In the examples illustrated in  FIG. 4  et seq. in which the temperature sensor TES and a transistor device are integrated in the same semiconductor body  100 , the control circuit may be configured to switch off the transistor when the current measurement signal S ICE  indicates that the temperature in the semiconductor body has reached a predefined temperature threshold. In this case, the control circuit may simply compare the current measurement signal S ICE  with a value that represents the temperature threshold in order to decide whether to switch off the transistor device or not. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.