Semiconductor device

Abstract

To provide a voltage fluctuation detection circuit capable of being integrated in a gate driver IC and a semiconductor device constituting such a voltage fluctuation detection circuit.SOLUTION: A voltage fluctuation detection circuit 10 is a voltage fluctuation detection circuit for detecting voltage fluctuation at a predetermined voltage detection point, and including a transistor Tr including a junction FET having RESURF structure, and a capacitance element C whose one end is connected to the transistor Tr and the other end is connected to a reference potential.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention , half relates to a conductor device.

Background Art

[0002] A power conversion circuit (for example, an inverter) including a high-side switch connected to a high-voltage source (DC input power supply Vin) and a low-side switch connected to the high-side switch is known. In such a power conversion circuit, in order to prevent a large through-current from flowing when both switches are turned on simultaneously, a period (dead time) during which both switches are turned off is provided between when one switch is turned off and the other switch is turned on. However, since the dead time is a period in which losses are generated and it is preferably made as short as possible, conventionally, a power conversion circuit that detects the dead time by detecting voltage fluctuations at the connection point (voltage detection point) between the high-side switch and the low-side switch and controls the dead time is known (see, for example, Patent Document 1).

[0003] As shown in FIG. 7, the power conversion circuit described in Patent Document 1 includes a voltage fluctuation detection circuit (hereinafter referred to as a conventional voltage fluctuation detection circuit 900) having a capacitive element 920 with one end connected to the connection point N between the high-side switch Q1 and the low-side switch Q2 and the other end connected to the reference potential (GND) via a resistor R, and detects the dead time by detecting voltage fluctuations at the connection point N as the voltage detection point. As the capacitive element 920 of the voltage fluctuation detection circuit 900, it is necessary to use one with a relatively high withstand voltage in consideration of the case where a large amount of power flows from the DC input power supply Vin, and generally an external one is used. In such a power conversion circuit, the high-side switch Q1 and the low-side switch Q2 are arranged in a high-voltage region, and a gate driver IC having a drive circuit or the like for driving each switch is arranged in a relatively low-voltage region.

[0004] According to the conventional voltage fluctuation detection circuit 900, when a voltage fluctuation occurs at the voltage detection point N, a displacement current flows through the capacitive element 920. Therefore, the voltage fluctuation can be detected by detecting the displacement current, and thus the dead time can be detected.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, in recent years, with the demand for miniaturization of electronic devices, it has been required to incorporate a voltage fluctuation detection circuit (capacitive element) for detecting dead time into a gate driver IC. In this case, it is necessary to form the capacitive element 920 constituting the voltage fluctuation detection circuit 900 on a semiconductor substrate. Therefore, it is conceivable to form a conductive film 970 disposed via an insulating film 950 on the semiconductor substrate 910 and an electrode 980 disposed via a relatively thick insulating film 990 on the conductive film 970, and to configure the capacitive element 920 with the conductive film 970, the relatively thick insulating film 990, and the electrode 980 (see FIG. 8).

[0007] However, in the manufacturing process of the gate driver IC, it is difficult to form a highly reliable and thick insulating film on the semiconductor substrate 910. Therefore, it is difficult to form a high-voltage withstand capacitor element on the semiconductor substrate 910, and there is a problem that it is difficult to incorporate the conventional voltage fluctuation detection circuit 900 into the gate driver IC. If an oxide film formed by the thermal oxidation method is used as the dielectric (insulating film 990) in the capacitor element 920, a high-quality oxide film can be formed, but it is difficult to form it thickly, and it is difficult to form a high-voltage withstand capacitor element that can withstand the voltage from the DC input power supply Vin. Also, if an oxide film formed by the normal temperature or plasma CVD method is used as the dielectric (insulating film 990) in the capacitor element 920, although it can be formed relatively thickly, the oxide film formed by the normal temperature or plasma CVD method is likely to have problems such as poor insulation, and it is difficult to form a highly reliable capacitor element.

[0008] Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to provide a voltage fluctuation detection circuit that can be incorporated into a gate driver IC and a semiconductor device constituting such a voltage fluctuation detection circuit.

Means for Solving the Problems

[0009] The voltage fluctuation detection circuit of the present invention is a voltage fluctuation detection circuit that detects voltage fluctuations at a predetermined voltage detection point, and includes a transistor including a junction FET having a RESURF structure connected to the voltage detection point, and a capacitor element having one end connected to the transistor and the other end connected to a reference potential.

[0010] The semiconductor device of the present invention includes a semiconductor substrate of a first conductivity type, a semiconductor base having a first semiconductor layer of a second conductivity type formed on the substrate, a first electrode disposed above the semiconductor base and in contact with the semiconductor base, a second electrode disposed at a position separated from the first electrode above the semiconductor base, an element isolation film formed in a predetermined region between the first electrode and the second electrode on the surface of the semiconductor base, an insulating film disposed between the second electrode and the element isolation film on the surface of the semiconductor base, a third electrode disposed on the insulating film at a position in contact with the element isolation film, and a conductive film disposed on the insulating film at a position separated from the third electrode. A transistor including a junction FET having a RESURF structure is constituted by the substrate, the first semiconductor layer, the element isolation film, the first electrode, and the third electrode, and a capacitor element is constituted by the first semiconductor layer, the insulating film, and the conductive film.

[0011] According to the voltage detection circuit and the semiconductor device of the present invention, since a transistor including a junction FET having a RESURF structure is provided, even when a large current flows from a DC input power source connected via a high-side switch, while maintaining a high breakdown voltage with the RESURF structure, the voltage on the source electrode side (the third electrode and the first conductive film side) of the transistor can be suppressed low by the junction FET (see FIG. 3), and the voltage applied to the capacitor element can be suppressed low. Therefore, it is not necessary to form a high-breakdown voltage capacitor element on the semiconductor substrate, and it is sufficient to form a low-breakdown voltage capacitor element. Thus, in the manufacturing process of the gate driver IC, a capacitor element can be formed on the semiconductor substrate, and the voltage fluctuation detection circuit can be incorporated into the gate driver IC.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the voltage fluctuation detection circuit and the semiconductor device of the present invention will be described based on the embodiments shown in the drawings. Note that each drawing is a schematic diagram and does not necessarily strictly reflect actual dimensions.

[0014] [Embodiment 1] 1. Configuration of the power conversion circuit 1 in Embodiment 1 and the voltage fluctuation detection circuit 10 according to Embodiment 1 First, the power conversion circuit 1 in which the voltage fluctuation detection circuit 10 according to Embodiment 1 is provided will be described. FIG. 1 is a diagram shown to explain the power conversion circuit 1 in Embodiment 1. Note that reference numeral R indicates a shunt resistor. As shown in FIG. 1, the power conversion circuit 1 is composed of a main circuit C1 and a switch control circuit C2 having the voltage fluctuation detection circuit 10 according to Embodiment 1.

[0015] The main circuit C1 includes a high-side switch Q1 connected to the DC input power supply Vin, and a low-side switch Q2 with one end connected to the high-side switch Q1 and the other end connected to the reference potential. An output terminal OUT is provided and connected to the connection point N of the high-side switch Q1 and the low-side switch Q2. The main circuit C1 operates with the first power supply voltage supplied from the DC input power supply Vin. As the high-side switch Q1 and the low-side switch Q2 of the main circuit C1, appropriate switch elements can be used. In Embodiment 1, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used.

[0016] The switch control circuit C2 controls the on / off of the high-side switch Q1 and the low-side switch Q2. The switch control circuit C2 includes an oscillation circuit 2, a voltage fluctuation detection circuit 10 according to Embodiment 1, a detection circuit 3, and an on / off control circuit 4. In the switch control circuit C2, power is supplied from power supplies Vcc and Vb different from the DC input power supply Vin, and it operates with a second power supply voltage lower than the first power supply voltage.

[0017] The oscillation circuit 2 sets the switching frequency and sends a signal to turn off the switch at a predetermined timing based on the set switching frequency to the on / off control circuit 4.

[0018] The voltage fluctuation detection circuit 10 according to Embodiment 1 is a voltage fluctuation detection circuit that detects the voltage fluctuation (voltage fluctuation per unit time, i.e., the differential value) at the connection point N of the main circuit C1. The voltage fluctuation detection circuit (differential circuit) 10 detects the voltage fluctuation at the voltage detection point N and sends the detection result to the detection circuit 3. Details of the voltage fluctuation detection circuit 10 will be described later.

[0019] The detection circuit 3 detects the timing when the voltage rise at the voltage detection point (connection point N) detected by the voltage fluctuation detection circuit 10 stops and the timing when the voltage drop stops, and sends a signal to the on / off control circuit 4.

[0020] The on-off control circuit 4 controls the on-off of the high-side switch Q1 and the low-side switch Q2 based on the signals from the oscillation circuit 2 and the detection circuit 3. The on-off control circuit 4 includes two RS flip-flop circuits RS-FF1 and RS-FF2 and a driver 5. The set terminal (S) of RS-FF1 is connected to the detection circuit 3, the reset terminal (R) is connected to the oscillation circuit 2, and the output terminal is connected to the input terminal HIN of the driver 5. The set terminal (S) of RS-FF2 is connected to the detection circuit 3, the reset terminal (R) is connected to the oscillation circuit 2, and the output terminal is connected to the input terminal LIN of the driver 5.

[0021] The driver 5 includes a high-side switch control circuit 6 that is connected to the gate electrode of the high-side switch Q1 at the terminal HO and controls the on-off of the high-side switch Q1 based on the signal input from the input terminal HIN, and a low-side switch control circuit 7 that is connected to the gate electrode of the low-side switch Q2 via the output terminal LO and controls the on-off of the low-side switch Q2 based on the signal input from the input terminal LIN. The driver 5 is provided with input terminals HIN and LIN, output terminals HO and LO, a switch input / output terminal VS, and power supply terminals Vcc and Vb.

[0022] By the way, when a voltage fluctuation detection circuit is composed only of a capacitive element as in the conventional voltage fluctuation detection circuit 900 (see FIG. 7), it is difficult to form a highly reliable and thick insulating film on a semiconductor substrate. Therefore, it is difficult to form a high-voltage-resistant capacitive element on a semiconductor substrate and incorporate it into a gate driver IC. Therefore, in the voltage fluctuation detection circuit 10 according to Embodiment 1, a voltage fluctuation detection circuit in which a transistor Tr including a junction FET having a RESURF structure and a capacitive element C are connected in series is used.

[0023] The transistor Tr is a junction FET having a RESURF structure and is connected to the voltage detection point (connection point N, OUT terminal) (see FIG. 2). The transistor Tr is a normally-on type semiconductor switch in which the drain electrode D is connected to the voltage detection point (connection point N) and the source electrode S is connected to the capacitor element C. The gate electrode is connected to the reference potential, and the transistor Tr does not perform a switching operation.

[0024] One end of the capacitor element C is connected to the transistor Tr, and the other end is connected to the reference potential via the resistor R. The voltage fluctuation detection circuit 10 according to the first embodiment detects the voltage fluctuation of the voltage detection point N that operates with the high-voltage first power supply voltage. However, since a voltage drop occurs in the junction FET having the RESURF structure of the transistor Tr, the voltage applied to the capacitor element C becomes relatively small (see FIG. 4). For this reason, the withstand voltage of the capacitor element C may be relatively low, and one having a level of several tens of V can be used.

[0025] As the voltage fluctuation detection circuit of the present invention, voltage fluctuation detection circuits of various configurations can be used. However, in the first embodiment, in order to enable it to be incorporated in the gate driver IC, as the voltage fluctuation detection circuit 10, a semiconductor device 100 according to the first embodiment in which the transistor Tr and the capacitor element C are formed on the same semiconductor substrate is used.

[0026] 2. Configuration of the semiconductor device 100 according to the first embodiment FIG. 2 is a cross-sectional view showing the semiconductor device 100 in Embodiment 1. In FIG. 2, reference numeral SR indicates a separation region. As shown in FIG. 2, the semiconductor device 100 according to Embodiment 1 includes a semiconductor substrate 110, a first electrode 120, a first field plate 122, a second electrode 130, an element isolation film 140, an insulating film 150, a third electrode 160, a second field plate 162, an external connection portion 164, and a conductive film 170. Although not shown in the figure, the semiconductor device 100 according to Embodiment 1 is formed on, for example, the same semiconductor substrate as at least a part of the elements constituting the driver 5 of the on-off control circuit 4 and is incorporated in the gate driver IC. Hereinafter, the region constituting the JFET as the transistor Tr is defined as a first region A1, and the region constituting the capacitor element C is defined as a second region A2.

[0027] The semiconductor substrate 110 has a p - -type substrate 111, an n - -type first semiconductor layer 112 formed on the substrate 111, a p - -type second semiconductor layer 113 disposed between the first semiconductor layer 112 and the element isolation film 140, and an n + -type first contact region CR1 formed in a region in contact with the first electrode 120. The impurity concentration of the second semiconductor layer 113 is substantially the same as the impurity concentration of the substrate 111. Further, the impurity concentration of the first contact region CR1 is higher than the impurity concentration of the first semiconductor layer 112.

[0028] The first electrode 120 is disposed at a predetermined position above the first region A1 in the semiconductor substrate 110 and is in contact with the semiconductor substrate 110 (contact region CR1). The first electrode 120 constitutes the drain electrode of the transistor Tr and is connected to a voltage detection point (connection point N) disposed in a first circuit that operates with a first power supply voltage. The first electrode 120 is made of metal (for example, aluminum).

[0029] The first field plate 122 is formed to cover the insulating film 152 and the element isolation film 140 from the surface of the insulating film 152 to the surface of the element isolation film 140, and is connected to the first electrode 120. In Embodiment 1, the first field plate 122 is made of polysilicon, but may be made of a metal (e.g., aluminum), a silicide (e.g., a metal silicide such as aluminum silicide (AlSi) or nickel silicide (NiSi)), or other appropriate conductors.

[0030] The second electrode 130 is disposed at a position separated from the first electrode 120 above the semiconductor substrate 110 (a predetermined position above the second region A2). The second electrode 130 is connected to the conductive film 170 on the semiconductor substrate 110 and is insulated from the semiconductor substrate 110 with the insulating film 150 interposed therebetween. The second electrode 130 is connected to a second circuit (such as the detection circuit 3) that operates at a second power supply voltage lower than the first power supply voltage.

[0031] The element isolation film 140 is formed in a predetermined region (specifically, most of the first region A1) between the first electrode 120 and the second electrode 130 on one surface of the semiconductor substrate 110. The element isolation film 140 is a LOCOS film made of SiO 2 and about half of its thickness is buried in the semiconductor substrate 110.

[0032] The insulating film 150 is disposed between the second electrode 130 and the element isolation film 140 on the surface of the semiconductor substrate 110. That is, the insulating film 150 is formed on the surface of the semiconductor substrate 110 in a part of the first region A1 and the entire second region A2. The insulating film 152 is disposed on the first electrode 120 side of the element isolation film 140 on the surface of the semiconductor substrate 110 when viewed in cross section. That is, the insulating film 152 is formed on the surface of the semiconductor substrate 110 in a part of the first region A1. The insulating films 150 and 152 are thermal oxide films.

[0033] The third electrode 160 is a film-like member disposed on the insulating film 150 at a position in contact with the element isolation film 140 (hereinafter, the third electrode 160 may also be referred to as the third electrode film 160). Note that, in Embodiment 1, the third electrode 160 is a film-like member, but it may not be a film-like member. The second field plate 162 is connected to the third electrode film 160 and is formed on the element isolation film 140 across the surface of the element isolation film 140. In Embodiment 1, the third electrode film 160 and the second field plate 162 are made of polysilicon, but they may be made of a metal (e.g., aluminum), a silicide (e.g., a metal silicide such as aluminum silicide (AlSi) or nickel silicide (NiSi)), or any other appropriate conductor. The external connection portion 164 is disposed on the second field plate 162 and is connected to the second field plate 162. The external connection portion 164 is connected to the outside at a reference potential. The external connection portion 164 is made of a metal (e.g., aluminum).

[0034] The conductive film 170 is disposed on the insulating film 150 at a position spaced apart from the third electrode film 160. The conductive film 170 is a polysilicon layer formed in a layered manner in a predetermined region of the second region A2 and is connected to the second electrode 130. The conductive film 170 faces the semiconductor substrate 110 with the insulating film 150 interposed therebetween.

[0035] In the first region A1, a transistor Tr (JFET) is formed by the substrate 111, the first semiconductor layer 112, the second semiconductor layer 113, the element isolation film 140, the first electrode 120, and the third electrode 160 of the semiconductor substrate 110. In the second region A2, a capacitor element C is formed by the first semiconductor layer 112, the insulating film 150, and the conductive film 170 of the semiconductor substrate 110. Note that, in the transistor Tr, the substrate 111, the first semiconductor layer 112, and the second semiconductor layer 113 have a RESURF structure in which depletion layers extend in the vertical direction from the pn junction surface between the substrate 111 and the first semiconductor layer 112 and depletion layers extend in the vertical direction from the pn junction surface between the first semiconductor layer 112 and the second semiconductor layer 113.

[0036] FIG. 3 is a schematic graph showing the RESURF structure of the semiconductor device 100 in Embodiment 1. In FIG. 3, the horizontal axis represents the voltage applied to the drain electrode (first electrode 120) of the transistor Tr, and the vertical axis represents the voltage applied to the source electrode of the transistor Tr (the voltage in the region of the semiconductor substrate 110 below the second electrode 130). In the transistor Tr, since the substrate 111, the first semiconductor layer 112, and the second semiconductor layer 113 form a RESURF structure, as shown in FIG. 4 to be described later, in the n-type first semiconductor layer 112, equipotential lines extending laterally on the side of the first electrode 120 connected to the high-voltage circuit extend vertically at relatively equal intervals as they go toward the third electrode side. Therefore, the potential decreases for each equipotential line in the first semiconductor layer 112, and the potential decreases as it goes from the first electrode 120 side to the third electrode 160 side. As a result, the potential in the vicinity of the third electrode 160 or the second electrode 130, which is the source electrode, is at least one digit smaller than the potential of the first electrode 120 (drain electrode). For example, as shown in FIG. 3, when a voltage of 600 V is applied to the first electrode 120, the voltage at the position of the third electrode 160 drops to 20 V. Since the electric field strength tends to be uniform and the maximum electric field strength decreases, in the first region A1, a semiconductor device having a high breakdown voltage is obtained.

[0037] 3. About Test Examples This test example is to confirm that by providing a transistor including a junction FET having a RESURF structure, even when a large current flows into the first electrode, the voltage on the source electrode side (the third electrode and conductive film side) of the transistor Tr can be kept low. FIG. 4 is a diagram schematically showing equipotential lines represented based on the simulation results for the semiconductor device 100a according to the embodiment.

[0038] (1) Example The semiconductor device 100a according to the embodiment is a semiconductor device having the same configuration as the semiconductor device 100 according to Embodiment 1, except for the following points: (A) The second electrode 130a and the conductive film 170a are on the element isolation film 140, and a capacitive element is formed facing the semiconductor substrate 110 with the element isolation film 140 interposed therebetween (the third electrode also serves as the second electrode); (B) A plurality of field plates FP are formed between the first electrode 120 and the second electrode 130a on the element isolation film 140 as seen in cross section; (C) The second semiconductor layer 113a is formed only in a part of the region in contact with the element isolation film 140 below the element isolation film 140; and (D) A dummy electrode Dummy is formed on the side of the second electrode 130a opposite to the first electrode 120 side.

[0039] (2) Simulation method A voltage of about 600 V was applied to the first electrode 120 of the semiconductor device 100a according to the embodiment, the substrate 111 and the second electrode 130a were set to 0 V, the potential in the semiconductor substrate 110 was calculated by simulation, the potential was plotted on the cross-sectional view of the semiconductor device 100a according to the embodiment based on the calculation result, and equipotential lines were drawn (see FIG. 4).

[0040] (3) Evaluation results p - -type substrate 111 and p - -type second semiconductor layer 113, the n -In the first semiconductor layer 112 of the [[ID=]], equipotential lines that extend horizontally on the side of the first electrode 120 connected to the high-voltage circuit become to extend vertically at relatively equal intervals as they go toward the third electrode side. Therefore, the potential decreases for each equipotential line in the first semiconductor layer 112, and the potential decreases from the first electrode 120 side toward the third electrode 160 side. And it was found that in the semiconductor substrate 110 under the third electrode 160, the potential has dropped to 100 V or less (about 20 V). Therefore, by providing a transistor including a junction FET having a RESURF structure, even when a large amount of power flows into the first electrode, the voltage on the source electrode side (the third electrode and the first conductive film side) of the transistor can be suppressed low (for example, one digit lower) by the junction FET. From this, it has been found that in the present invention, a capacitive element with a relatively low breakdown voltage (for example, 100 V or less) can be used.

[0041] 4. Effects of the voltage fluctuation detection circuit 10 and the semiconductor device 100 according to Embodiment 1 According to the voltage fluctuation detection circuit 10 and the semiconductor device 100 according to Embodiment 1, since a transistor Tr including a junction FET having a RESURF structure is provided, even when a large amount of power flows from the DC input power supply Vin connected via the high-side switch Q1, while maintaining a high breakdown voltage with the RESURF structure, the voltage on the source electrode side (the third electrode side) of the transistor Tr can be suppressed low by the junction FET, and the voltage applied to the capacitive element C can be suppressed low. Therefore, since it is not necessary to form a capacitive element with a high breakdown voltage, the capacitive element C can be formed on the semiconductor substrate in the manufacturing process of the gate driver IC, and as a result, the voltage fluctuation detection circuit can be incorporated into the gate driver IC.

[0042] Further, according to the semiconductor device 100 according to Embodiment 1, the first electrode 120 is connected to a voltage detection point (connection point N) arranged in a main circuit C1 (first circuit) operating with a first power supply voltage, and the second electrode 130 is connected to a switch control circuit C2 (second circuit) operating with a second power supply voltage lower than the first power supply voltage. Therefore, it becomes a semiconductor device in which the high-voltage main circuit C1 and the low-voltage switch control circuit C2 are arranged on the same semiconductor substrate. Further, voltage fluctuations at the voltage detection point N of the high-voltage main circuit C1 can be detected by a voltage fluctuation detection circuit configured in the low-voltage switch control circuit C2.

[0043] Further, according to the semiconductor device 100 according to Embodiment 1, since a transistor Tr including a junction FET having a RESURF structure is configured by the substrate 111, the first semiconductor layer 112, and the second semiconductor layer 113 of the semiconductor substrate 110, the element isolation film 140, the first electrode 120, and the third electrode 160, even when a large amount of power flows from a DC input power supply Vin connected via a high-side switch Q1, a high breakdown voltage can be maintained by the RESURF structure composed of the substrate 111 and the first semiconductor layer 112. Further, since a voltage drop occurs due to the JFET having a RESURF structure, the potential on the source electrode side (third electrode side) of the transistor Tr can be kept low. Therefore, the voltage applied to the capacitor element C can be kept low, and it is not necessary to form a capacitor element with a high breakdown voltage. As a result, since the capacitor element C can be formed on the semiconductor substrate in the manufacturing process of the gate driver IC, it becomes possible to incorporate the voltage fluctuation detection circuit into the gate driver IC.

[0044] Further, according to the semiconductor device 100 according to Embodiment 1, since the transistor Tr including the junction FET having a RESURF structure is configured by the substrate 111, the first semiconductor layer 112, the second semiconductor layer 113, the element isolation film 140, the first electrode 120, and the third electrode 160 of the semiconductor substrate 110, in the RESURF structure, a voltage drop occurs, and the potential on the source electrode side (third electrode side) of the transistor Tr can be suppressed low by the junction FET. Therefore, a part of the main circuit C1 having a relatively high voltage and the switch control circuit C2 having a relatively low voltage can be connected on the same semiconductor substrate.

[0045] Further, according to the semiconductor device 100 according to Embodiment 1, since the third electrode 160 is connected to the reference potential, the input impedance is small, and a large current can flow through the semiconductor device 100 which is a junction FET. Further, since the third electrode 160 is connected to the reference potential, the semiconductor device 100 does not need to be controlled, and the semiconductor device 100 can be used as a passive element. Therefore, a driver circuit or the like for switching is not required, and the semiconductor device is miniaturized.

[0046] Further, according to the semiconductor device 100 according to Embodiment 1, since the second electrode 130 is connected to the conductive film 170 and is separated from the semiconductor substrate 110 with the insulating film 150 interposed therebetween, a capacitive element C having the insulating film 150 on the semiconductor substrate 110 as a dielectric between the electrodes can be formed. Therefore, since the capacitive element C can be formed on the semiconductor substrate on the semiconductor substrate 110, it becomes possible to incorporate a voltage fluctuation detection circuit into the gate driver IC.

[0047] [Embodiment 2] FIG. 5 is a cross-sectional view showing to explain the semiconductor device 101 according to Embodiment 2. The semiconductor device 101 according to Embodiment 2 basically has the same configuration as the semiconductor device 100 according to Embodiment 1, but the configuration of the capacitive element C is different from that of the semiconductor device 100 according to Embodiment 1.

[0048] As shown in FIG. 5, the semiconductor substrate 110 has a separation region 114 provided so as to divide the first semiconductor layer into a first region 112a on the side of the third electrode film 160 and a second region 112b on the side of the conductive film 170a. That is, the first region A1 and the second region A2 are separated by the separation region 114.

[0049] The semiconductor device 101 according to Embodiment 2 includes a fourth electrode 180 disposed between the third electrode film 160 and the conductive film 170b. The fourth electrode 180 is connected to the first region 112a of the first semiconductor layer through an n + -type third contact region CR3 formed on the surface of the semiconductor substrate 110 on one hand, and is connected to the conductive film 170b on the other hand. The fourth electrode 180 is insulated from the second region 112b. The second electrode 130b is connected to the second region 112b through an n + -type second contact region CR2 and is separated from the conductive film 170b through the insulating film 150. Therefore, the conductive film 170b, the insulating film 150, and the semiconductor substrate (second region 112b) constitute a capacitor element C. However, unlike Embodiment 1, the side of the conductive film 170b is at a high potential.

[0050] Thus, although the configuration of the capacitor element C in the semiconductor device 101 according to Embodiment 2 is different from that in the semiconductor device 100 according to Embodiment 1, similar to the case of the semiconductor device 100 according to Embodiment 1, since the transistor Tr including the junction FET having a RESURF structure is provided, even when a large power flows in from a DC input power source connected through a high-side switch, the potential on the source electrode side of the transistor Tr can be kept low by the junction FET while maintaining a high breakdown voltage with the RESURF structure, and the voltage applied to the capacitor element C can be kept low. Therefore, it is not necessary to form a high-breakdown-voltage capacitor element on the semiconductor substrate. As a result, since the capacitor element C can be formed on the semiconductor substrate 110 in the manufacturing process of the gate driver IC, it becomes possible to incorporate the voltage fluctuation detection circuit into the gate driver IC.

[0051] Also, according to the semiconductor device 101 according to Embodiment 2, since the semiconductor substrate 110 has the separation region 114 provided so as to divide the first semiconductor layer into the first region 112a on the side of the third electrode film 160 and the second region 112b on the side of the conductive film 170b, the region where the transistor Tr is formed and the region where the capacitor element C is formed can be separated. Therefore, it is possible to reliably prevent the influence when a high voltage is applied to the transistor Tr from reaching the capacitor element C.

[0052] Note that the semiconductor device 101 according to Embodiment 2 has the same configuration as the semiconductor device 100 according to Embodiment 1 except for the configuration of the capacitor element C, and thus has the corresponding effects among the effects of the semiconductor device 100 according to Embodiment 1.

[0053] [Embodiment 3] FIG. 6 is a cross-sectional view showing the semiconductor device 102 according to Embodiment 3 for explanation. The semiconductor device 102 according to Embodiment 3 basically has the same configuration as the semiconductor device 101 according to Embodiment 2, but the configuration of the first region A1 of the semiconductor substrate is different from that of the semiconductor device 101 according to Embodiment 2.

[0054] The semiconductor substrate 110 has a p-type region 115 (first conductivity type region) formed on the surface of the first region 112a, an n-type region 116 (second conductivity type region) formed separately from the first region 112a on a part of the surface of the p-type region 115, and an n-type channel region 117 formed on the surface of the p-type region 115, connected to the first region 112a of the first semiconductor layer at one end, and connected to the n-type region 116 at the other end. The fourth electrode 180 is in contact with the n-type region 116 through the third contact region CR3. That is, the transistor Tr of the semiconductor device 102 according to Embodiment 3 constitutes a depletion-type MOSFET.

[0055] The third electrode film 160 faces the channel region 117 through the insulating film 150, and by changing the voltage of the third electrode film 160, the voltage applied to the fourth electrode 180, and thus the capacitor element C, can be controlled.

[0056] As described above, although the configuration of the first region A1 of the semiconductor device 102 according to Embodiment 3 is different from that of the semiconductor device 101 according to Embodiment 2, the semiconductor device 102 according to Embodiment 3 includes a transistor Tr including a junction FET having a RESURF structure, similar to the case of the semiconductor device 101 according to Embodiment 2. Therefore, even when a large amount of power flows in from a DC input power source connected via a high-side switch, the RESURF structure can maintain a high breakdown voltage while the voltage on the source electrode side of the transistor Tr can be kept low by the junction FET, and the voltage applied to the capacitive element C can be kept low. Accordingly, it is not necessary to form a capacitive element with a high breakdown voltage. As a result, in the manufacturing process of the gate driver IC, since the capacitive element C can be formed on the semiconductor substrate, it becomes possible to incorporate a voltage fluctuation detection circuit into the gate driver IC.

[0057] Further, the semiconductor device 102 according to Embodiment 3 includes a p-type region 115 formed on the surface of the first region 112a, an n-type region 116 formed separately from the first region 112a on a part of the surface of the p-type region 115, and an n-type channel region 117 formed on the surface of the p-type region 115, connected to the first region 112a at one end, and connected to the n-type region 116 at the other end, which constitutes a depletion-type MOSFET. With such a configuration, by changing the voltage applied to the third electrode 160, the charging voltage of the capacitive element C can be adjusted. As a result, the semiconductor device can finely control the voltage applied to the capacitive element.

[0058] Note that the semiconductor device 102 according to Embodiment 3 has the same configuration as the semiconductor device 101 according to Embodiment 2 in points other than the configuration of the first region A1 of the semiconductor substrate, and thus has corresponding effects among the effects that the semiconductor device 101 according to Embodiment 2 has.

[0059] As described above, the present invention has been explained based on the above embodiments. However, the present invention is not limited to the above embodiments. It can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

[0060] (1) The number, material, shape, position, size, etc. of the components described in the above embodiments are examples, and can be changed within a range that does not impair the effects of the present invention.

[0061] (2) In each of the above embodiments, the third electrode was connected to the reference potential and the semiconductor device 100 was not controlled. However, the present invention is not limited to this. An appropriate voltage may be applied to the third electrode to control the potential within the semiconductor device 100.

[0062] (3) In each of the above embodiments, the second semiconductor layer 113 was disposed entirely between the first semiconductor layer 112 and the element isolation film 140. However, the present invention is not limited to this. The second semiconductor layer 113 may be disposed only in a part between the first semiconductor layer 112 and the element isolation film 140, or the second semiconductor layer 113 may not be disposed.

[0063] (4) In each of the above embodiments, a shunt resistor was used to detect the displacement current of the capacitive element of the voltage fluctuation detection circuit as a voltage. However, the present invention is not limited to this. An appropriate detector such as a Hall element or a current transformer may be used.

Explanation of Reference Numerals

[0064] 10... voltage fluctuation detection circuit, 100, 100a, 101, 102... semiconductor device, 110... semiconductor substrate, 111... substrate, 112... first semiconductor layer, 112a... first region, 112b... second region, 113, 113a...... second semiconductor layer, 114... isolation region, 115... p-type region, 116... n-type region, 117... channel region, 120... first electrode, 130... second electrode, 130a... second electrode, 140... element isolation film, 150... insulating film, 160... third electrode (third electrode film), 170, 170a... conductive film, 180... fourth electrode

Claims

1. a semiconductor body having a substrate of a first conductivity type and a first semiconductor layer of a second conductivity type formed on the substrate; a first electrode disposed above the semiconductor body, in contact with the semiconductor body, and connected to the first semiconductor layer; a second electrode disposed above the semiconductor substrate at a position spaced apart from the first electrode; an isolation film formed in a predetermined region between the first electrode and the second electrode on the surface of the semiconductor substrate; an insulating film disposed between the second electrode and the element isolation film on the surface of the semiconductor substrate in a top view; a third electrode disposed on the insulating film at a position in contact with the element isolation film; a conductive film disposed on the insulating film at a position spaced apart from the third electrode, a RESURF structure is formed by the substrate and the first semiconductor layer of the semiconductor base, a transistor including a junction FET having a RESURF structure is configured by the substrate of the semiconductor base, the first semiconductor layer, the element isolation film, the first electrode, and the third electrode, a first semiconductor layer of the semiconductor substrate, the insulating film, and the conductive film forming a capacitance element;

2. the first electrode is connected to a voltage detection point disposed in a first circuit that operates with a first power supply voltage; 2. The semiconductor device according to claim 1, wherein the second electrode is connected to a second circuit that operates on a second power supply voltage that is lower than the first power supply voltage.

3. 3. The semiconductor device according to claim 1, wherein the third electrode is connected to a reference potential.

4. 4. The semiconductor device according to claim 1, wherein the second electrode is connected to the conductive film and is separated from the semiconductor substrate with the insulating film interposed therebetween.

5. the semiconductor substrate further includes a separation region provided so as to divide the first semiconductor layer into a first region on the third electrode side and a second region on the conductive film side; the second electrode is in contact with the second region and is spaced apart from the conductive film; 4. The semiconductor device according to claim 1, further comprising a fourth electrode between the third electrode and the conductive film, the fourth electrode being insulated from the second region, in contact with the first region, and connected to the conductive film.

6. the semiconductor substrate further includes a separation region provided to divide the first semiconductor layer into a first region on the third electrode side and a second region on the conductive film side, a first conductivity type region formed on a surface of the first region, a second conductivity type region formed on a part of the surface of the first conductivity type region so as to be spaced apart from the first region, and a second conductivity type channel region formed on the surface of the first conductivity type region, connected to the first region at one end and connected to the second conductivity type region at the other end; the second electrode is in contact with the second region and is spaced apart from the conductive film; The semiconductor device according to any one of claims 1 to 3, further comprising a fourth electrode between the third electrode and the conductive film, the fourth electrode being insulated from the second region, in contact with the second conductivity type region, and connected to the conductive film.

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