JP2006202987A - Manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize improvement in both of the S/N of a JFET and the transient characteristics of drain current simultaneously, in a semiconductor device equipped with the JFET used for a microphone or the like. <P>SOLUTION: In the manufacturing method of a semiconductor device, a JFET210 as a variable impedance element is connected between the gate of a main JFET100 and a source. In the transition period just after impressing a drain voltage, the channel impedance of the JFET210 is low so that the transitional drain current may be promptly absorbable. On the other hand, after the drain current is in a steady state, the channel impedance of the JFET210 is made high-impedance so as to attain low noise by reducing leak (useless electric discharge) of a signal component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device for a microphone including a junction field effect transistor in which an electret capacitor is connected between a gate and a source and a manufacturing method thereof.

  An electret condenser microphone (ECM) is an acoustoelectric conversion device that converts sound into an electric signal. In ECM, a polymer film (Teflon film or the like) is electretized to maintain charging, and it is not necessary to supply a capacitor voltage from the outside, thereby reducing the size and thickness of the apparatus.

  An electret capacitor is a junction field effect transistor as an amplifying element and an impedance conversion element (JFET: a transistor that controls a drain current using a depletion layer formed by a PN junction of a semiconductor or a Schottky barrier formed by contact between a metal and a semiconductor) Connected between the gate and source.

  FIG. 11 is a circuit diagram showing a general configuration of a JFET for a microphone.

  As shown in the figure, a resistance element 502 formed of polysilicon or the like is connected between the gate and source of the JFET 500 for early stabilization of a transient drain current when the power is turned on.

  FIG. 12 is a circuit diagram showing an equivalent circuit of an electret condenser microphone (ECM).

As shown in the figure, the ECM includes an electret capacitor 34 (functioning as an acoustoelectric conversion element M), a JFET 31, and a resistance element 33 connected between the source and gate of the JFET. The ECM is supplied with a power supply voltage from a power supply 38, and the power supply voltage is turned on / off by a switch 37. The resistor 35 and the capacitor 36 constitute a time constant circuit for suppressing a steep voltage change when the power is turned on / off.

  When the switch 37 is closed and the power is turned on, a transient drain current (Id) flows through the JFET 31 instantaneously.

  Here, it is assumed that there is no resistor 33 connected between the gate and source of the JFET. In this case, the transient drain current (including a high-frequency component because the voltage fluctuates) is transmitted to the gate of JFET 31 via the electret capacitor (M).

  In the absence of the resistor 33, the gate of the JFET 31 is in a floating state, so that it is not possible to actively absorb the potential fluctuation of the gate due to the transient current component.

  Therefore, a considerable time (for example, 5 to 10 seconds) is required until the drain current (Id) becomes steady and the gate potential of the JFET 31 is stabilized. For this reason, also in the inspection after assembling the microphone, it takes time for the drain current to reach a steady state before the measurement, which causes inconveniences such as a decrease in the efficiency of the inspection process.

  As a countermeasure, when a resistor 33 is connected between the gate and source of the JFET 31 as shown in FIG. 12, the transient drain current (Id) passes through a path as indicated by a thick solid line arrow in the figure. Therefore, the drain current transient response converges in a short time.

  Specifically, when the resistance 33 is high resistance, the transient response period is, for example, about 2 seconds. By reducing the resistance of the resistor 33, the transient response period can be shortened to about 0.1 seconds.

An ECM including a JFET in which a resistor is connected between a gate and a source as shown in FIG.
JP 61-160963 A

  As described above, by lowering the resistance value of the resistor connected between the gate and source of the JFET, the effect of absorbing (pushing) a transient drain current when the power is turned on is enhanced, and the gate potential of the JFET is quickly stabilized. This is advantageous in terms of improving the transient characteristics.

  However, if the resistance value of the resistor connected between the gate and source of the JFET is lowered, this time, the signal component that conveys the potential change of the electret capacitor escapes to the ground through the resistor during normal operation of the ECM. (That is, the resistor functions as a damping resistor), and as a result, the ECM noise is increased (deteriorating the S / N ratio).

  In other words, a decrease in the resistance value of the resistor connected between the gate and source of the JFET is effective for improving the transient characteristics, but on the other hand, an increase in the noise of the ECM (the JFET used in the normal operation). It is disadvantageous and the two are in a conflicting relationship (ie, a trade-off relationship).

  This contributes to the difficulty of ECM design.

  The present invention has been made in view of the above circumstances, and in a semiconductor device including a JFET used for a microphone or the like, both improvement of the transient characteristics of the drain current and improvement of the S / N ratio of the JFET are performed simultaneously. It aims to be realized.

  The semiconductor device of the present invention includes a junction field effect transistor (JFET) and a variable impedance element connected between the gate and source of the JFET.

  According to the above configuration, the impedance value of the variable impedance can be changed according to the operation state of the JFET, and a semiconductor device that can simultaneously improve the transient characteristics and noise characteristics, which has been impossible in the past, is realized. That is, the impedance of the variable impedance element is lowered at the beginning of power-on to improve the transient characteristics of the drain current. After the drain current is stabilized, the impedance of the variable impedance element is increased to improve the S / N ratio of the JFET. Can be made compatible.

  In the semiconductor device of the present invention, the variable impedance element is a JFET, the gate of the JFET is connected to the drain of the JFET, and one of the two signal terminals of the JFET is the terminal. Including one connected to the gate of the JFET and the other terminal connected to the source of the JFET.

  With this configuration, the JFET as a variable impedance element has a low impedance at the moment when the power is turned on, so that an effect that a transient drain current can be quickly absorbed is obtained. When the voltage is stabilized, a voltage is applied to the gate of the JFET, and the channel is closed to increase the impedance, so that an effect of suppressing the noise of the JFET is obtained. Since the impedance control of the variable impedance element is automatically performed, it is not necessary to supply a control signal from the outside, and the circuit configuration is simplified. Therefore, the size and thickness of the ECM are not hindered.

  In the semiconductor device of the present invention, the variable impedance element is a depletion type MOS field effect transistor (MOSFET), and the gate of the depletion type MOSFET is connected to the drain of the JFET. , One of two signal terminals of the depletion type MOSFET is connected to the gate of the JFET, and the other terminal is connected to the source of the JFET.

  When the (main) JFET as the amplifying element and the impedance conversion element and the JFET as the variable impedance element are integrated on one semiconductor substrate, it is difficult to ensure strict electrical insulation between the two JFETs due to its structure. is there. Here, a JFET as a variable impedance element is a depletion type MOSFET (which means an insulated gate field effect transistor, and includes an insulating film using a film other than an oxide film such as a dielectric film). By substituting for, electrical insulation of the gates of both FETs can be easily ensured. Also, in the case of MOSFET, unlike JFET, no gate current flows, and therefore there is an advantage that complete high resistance (resistance with infinite impedance) can be realized by controlling the gate voltage.

  In the semiconductor device of the invention, the variable impedance element may be a JFET or a depletion type MOSFET having a gate terminal to which a control voltage for impedance adjustment can be applied from the outside. .

  An independent gate terminal is provided in a JFET or MOSFET as a variable impedance element, and the gate voltage can be freely controlled from the outside. As a result, it is possible to freely control the impedance value, the timing of changing the impedance value, or the mode of the change, and a more accurate design can be performed. For example, when a specific signal component is input from a microphone, the variable impedance element can be reduced in impedance so that the component is released so that no sound is collected by the microphone.

  In another aspect of the semiconductor device of the present invention, a capacitive element is connected between the gate and source of the JFET.

  The present invention mainly assumes a semiconductor device for a microphone. However, the present invention is not necessarily limited to this, and a circuit having a configuration in which only a capacitive element (capacitance component) is connected between a gate and a source. Is applicable and clarifies this point.

  Another aspect of the semiconductor device of the present invention includes a semiconductor device used for a microphone, in which an electret capacitor that functions as an acoustoelectric conversion element is connected between the gate and source of the JFET.

  The ECM is widely used as a microphone for a portable terminal such as a cellular phone. In recent years, there has been a strong demand for its miniaturization, thinning, high performance, and low power consumption. An ECM using the present invention can satisfy these requirements.

  The electret condenser microphone of the present invention is configured by housing the semiconductor device and the electret condenser in the same casing.

  If a JFET or depletion type MOSFET is used as the variable impedance element and integrated with the original JFET, it is not necessary to form a high resistance made of polysilicon on the semiconductor substrate as in the prior art. The semiconductor device can be thinned. In recent years, with further reduction in size and weight of portable terminals, there is a strict demand for thinner ECM. The semiconductor device of the present invention contributes to thinning of the ECM.

  The method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device in which a JFET as a first transistor and a JFET as a second transistor functioning as a variable impedance element are integrated. A first step of forming a second conductive type semiconductor layer (53) on a first conductive type semiconductor substrate (51, 52) functioning as a gate of the first transistor; An isolation layer for introducing an impurity of the first conductivity type into the semiconductor layer (53) and isolating the second conductivity type semiconductor device (53) into the formation regions of the first and second transistors. (54a, 54b, 54c) and at the same time, a second step of forming a channel diffusion layer (55) of the second transistor, and the second step of forming the second conductivity type semiconductor layer (53). A third step of selectively introducing a first conductivity type impurity into the transistor formation region to form a first conductivity type diffusion region (57) functioning as a part of the gate of the JFET; An impurity having the second conductivity type is selectively introduced into each of the first and second transistor formation regions of the second conductivity type semiconductor layer (53), and the source layer (59 of the first transistor). ) And the drain layer (60) and at the same time, a fourth step of forming the gate layer (61a or 61b) of the second transistor as the variable impedance, and the electrode layers (63a, 63b, 63c, 63d) , 63e, 64).

  By this manufacturing method, the main JFET and the JFET as the variable impedance element can be efficiently formed on the same semiconductor substrate. In particular, in the fourth step, the source and drain layers (59, 60) of each JFET and the gate layer (61a, 61b) of the JFET as a variable impedance element can be simultaneously formed by selective impurity introduction. The number of processes can be reduced. Also, at this time, by appropriately controlling the gate length (L) and gate width (W) of the JFET as the variable impedance element, the characteristics of the variable impedance element can be adjusted with high accuracy to achieve the desired characteristics. Can do.

  According to the present invention, it is possible to change the impedance value of the variable impedance in accordance with the operation state of the JFET, thereby realizing a semiconductor device that can simultaneously improve the transient characteristics and the noise characteristics that were impossible in the past.

  That is, the impedance of the variable impedance element is lowered at the beginning of power-on to improve the transient characteristics of the drain current. After the drain current is stabilized, the impedance of the variable impedance element is increased to improve the S / N ratio of the JFET. Can be realized.

  Also, by adopting a circuit configuration in which the variable impedance element is composed of a JFET or a depletion type MOSFET, and the gate of the JFET or depletion type MOSFET (depletion type FET) is connected to the drain of the main JFET. Thus, it is possible to automatically perform appropriate control of the impedance of the variable impedance element.

  That is, at the moment when the power is turned on, since the depletion type FET as the variable impedance element has a low impedance, an effect that the transient drain current can be quickly absorbed is obtained. When the drain voltage is stabilized, a voltage is applied to the gate of the depletion type FET, and the channel is closed to increase the impedance, so that an effect of suppressing noise of the JFET can be obtained. Since automatic adjustment of the variable impedance is possible, it is not necessary to supply a control signal from the outside, the circuit configuration is simplified, and therefore, the ECM or the like is not hindered in size reduction or thickness reduction.

  Further, by using a depletion type MOSFET as a variable impedance element, electrical insulation between the gates of each FET can be easily ensured. Also, in the case of MOSFET, unlike JFET, no gate current flows, so there is also an advantage that complete high resistance (resistance with infinite impedance) can be realized by controlling the gate voltage.

  In addition, by providing an independent gate terminal to the JFET or depletion type MOSFET as a variable impedance element, it is possible to freely control the impedance value, the timing of changing the impedance value, or the mode of the change. Thus, a more accurate design can be performed. For example, when a specific signal component is input from a microphone, the variable impedance element can be reduced in impedance so that the component is released so that no sound is collected by the microphone.

  The present invention mainly assumes a semiconductor device for a microphone. However, the present invention is not necessarily limited to this, and only a capacitive element (capacitance component) is connected between a gate and a source. It can be widely applied to circuits.

  Further, the ECM is widely used as a microphone for a portable terminal such as a cellular phone, and in recent years, its miniaturization, thinning, and high performance are strongly demanded. An ECM using the present invention can satisfy these requirements.

  Further, when a JFET or a depletion type MOSFET is used as a variable impedance element and integrated with an original JFET, it is not necessary to form a high resistance made of polysilicon on a semiconductor substrate as in the prior art. Therefore, the semiconductor device can be thinned.

  In recent years, with further reduction in size and weight of portable terminals, there is a strict demand for thinner ECM. The semiconductor device of the present invention contributes to thinning of the ECM.

  Further, the main JFET and the JFET as the variable impedance element can be efficiently formed on the same semiconductor substrate by the method for manufacturing a semiconductor device of the present invention. In particular, by selectively introducing impurities, the source and drain layers of each JFET and the gate layer of the JFET as a variable impedance element can be formed simultaneously, and the number of processes can be reduced.

  Also, at this time, by appropriately controlling the gate length (L) and gate width (W) of the JFET as the variable impedance element, the characteristics of the variable impedance element can be adjusted with high accuracy to achieve the desired characteristics. Can do.

Embodiments of the present invention will be described below with reference to the drawings.
(Embodiment 1)

  FIG. 1 is a circuit diagram showing a basic circuit configuration of a semiconductor device of the present invention.

  The semiconductor device of the present invention is suitable for microphone use such as ECM (electret condenser microphone), and is connected between a JFET 100 and a gate (G) and a source (S) of the JFET 100 as shown. Variable impedance element 200.

  The variable impedance element 200 is composed of an active element (for example, a field effect transistor: FET). The impedance value is adaptively changed using the characteristics of the active element to realize both improvement of the transient characteristics of the drain current and improvement of the S / N ratio.

  As described with reference to FIG. 12, the smaller the resistance value of the gate-source resistance of the JFET, the more effective the drain current transient characteristics are. Therefore, the variable impedance element 200 has a low impedance when the power is turned on and the JFET 100 is turned on.

  In addition, after the drain current is stabilized, the variable impedance element 200 becomes high impedance, thereby reducing the leakage of the signal current.

  FIG. 2 is a circuit diagram showing an example of a specific circuit configuration of the semiconductor device of the present invention.

  In the semiconductor device of FIG. 2, the variable impedance element 210 is composed of a P-channel JFET or a depletion type P-channel MOSFET (hereinafter collectively referred to as a depletion type FET).

  A JFET (hereinafter referred to as a main JFET) 100 that performs signal amplification and impedance conversion is an N-channel JFET.

  The gate of the depletion type FET 210 is connected to the drain of the main JFET 100, the drain is connected to the gate of the main JFET 100, and the source is connected to the source of the main JFET 100.

  Before the semiconductor device is powered on, the channel resistance of the depletion type FET 210 is in a low impedance state (a state in which a channel is formed). Therefore, the transient drain current of the main JFET 100 that occurs immediately after power-on is quickly absorbed, and the transient characteristics of the drain current are improved.

  Next, when power is supplied to the semiconductor device, a drain voltage is applied to the main JFET 100, and a positive voltage is also applied to the gate (G) of the depletion type FET 210. By applying this positive voltage, the channel resistance of the depletion type FET 210 shifts from a low impedance to a high impedance (the channel is closed). This increase in impedance reduces the discharge (leakage) of normal signal components, so that the noise of the semiconductor device can be reduced.

  Thus, the variable impedance can be automatically adjusted by the circuit configuration of FIG. Therefore, it is not necessary to give a control signal from the outside, the circuit configuration is simplified, and it does not hinder the miniaturization and thinning of the ECM and the like.

  JFET is characterized by excellent response characteristics. On the other hand, when a depletion type MOSFET is used, there is an advantage that electrical insulation between the gate of the MOSFET as the variable impedance element and the gate of the main JFET can be easily secured. Also, in the case of MOSFET, unlike JFET, no gate current flows at all, so that complete high resistance (resistance with infinite impedance) can be realized by controlling the gate voltage.

  FIG. 3 is a circuit diagram showing another example of a specific circuit configuration of the semiconductor device of the present invention.

  3 has a structure in which the gate of an FET (JFET or MOSFET) 220 functioning as a variable impedance element is taken out as an independent terminal.

  By providing an independent gate terminal, it becomes possible to freely control the impedance value, the timing of changing the impedance value, or the mode of the change, and a more accurate design can be performed.

For example, when a specific signal component is input from a microphone, it is possible to use the variable impedance element with a low impedance so that the component is released so that sound is not collected by the microphone.
(Embodiment 2)

  In this embodiment, a method for manufacturing a semiconductor device will be described. The semiconductor device in the present embodiment is a complementary JFET semiconductor device (for example, a diagram) in which a pair of N-channel JFETs (main FETs) and P-channel JFETs (JFETs as variable impedance elements) of a pair of JFETs of different conductivity types are integrated. 2 circuit configuration).

4 to 9 are cross-sectional views of a semiconductor device for explaining main manufacturing steps of the semiconductor device of the present invention.
(First step: FIG. 4)

As shown in FIG. 4, a P-type epitaxial layer 52 is formed on a P ++ conductive type semiconductor substrate 51 by an epitaxial growth method using a well-known CVD method (thereby, a P functioning as a gate of the main JFET). Next, an N-type channel layer (N-type epitaxial layer) 53 is formed on the P-type semiconductor substrate by the same method. The N-type channel layer 53 may be formed using an ion implantation method.
(Second step: FIG. 5)

Next, as shown in FIG. 5, the N-type channel layer 53 is separated into a main JFET formation region (53a) and a JFET formation region (53b) by ion implantation (or vapor deposition) and heat treatment of boron (B). In addition, a separation layer (54a, 54b, 54c) is formed, and at the same time, a P-type channel diffusion layer (variable impedance channel layer: reference numeral 55) of JFET is formed. Subsequently, an oxide film 56 is formed on the surface of the N-type channel layer 53 by thermal oxidation.
(Third step: FIG. 6)

Next, as shown in FIG. 6, a predetermined region of the oxide film 56 is opened, a gate diffusion layer 57 is formed by ion implantation (or vapor deposition) of boron (B) and heat treatment, and an oxide film 58 is formed. To do.
(Fourth process: FIG. 7)

Next, as shown in FIG. 7, a predetermined region of the oxide film 58 is opened, and the source diffusion layer 59 and the drain diffusion layer 60 of the main JFET are formed by ion implantation (or vapor deposition) of phosphorus (P) and heat treatment, and Then, a gate layer (61a, 61b) of JFET as a variable impedance element is formed, and an oxide film 62 is formed.
(5th process: FIG. 8, FIG. 9)

  Next, as shown in FIG. 8, a predetermined region of the oxide film 62 is opened, and electrodes 63 (63a to 63e) are formed. Here, aluminum or the like is used as the electrode material. Further, a gate electrode 64 (of a main JFET) made of a metal such as aluminum is formed on the entire back surface of the P ++ conductivity type substrate 51. Each electrode (63a-63e, 64) is connected as shown in FIG. 2, for example.

  By this method, a semiconductor device having excellent characteristics including a main JFET and a JFET as a variable impedance element can be efficiently formed on the same semiconductor substrate.

  In addition, unlike the conventional process using the high resistance of polysilicon, the steps of polysilicon deposition and resistance formation by patterning are not required, and a variable impedance element can be easily formed. Further, the thickness of the semiconductor device can be reduced as much as polysilicon is not stacked on the substrate.

  In the fourth step, the source / drain layers (59, 60) of the main JFET and the gate layers (61a, 61b) of the JFET as variable impedance elements are simultaneously formed by selective impurity introduction. It is possible to reduce the number of processes.

In addition, by appropriately controlling the gate length (L) and gate width (W) of the JFET as the variable impedance element, the characteristics of the variable impedance element can be adjusted with high accuracy and desired impedance characteristics can be realized. .
(Embodiment 3)

  FIG. 10 is a view for explaining a mounting structure of an electret condenser microphone (ECM) on which the semiconductor device of the present invention is mounted.

  In FIG. 10, an electret capacitor 300 includes an electret film 304, a vibration film 306, a vibration ring 308, a conductive washer 310, a gate ring 312 formed on the back surface of a closing plate (part of the casing) 302, Consists of.

  The semiconductor device 400 includes an integrated circuit including two JFETs (100, 210) shown in FIG.

  Reference numeral 320 is a part of the outer casing made of a conductive material. Reference numeral 330 is a common electrode. T1 to T3 are printed wiring conductors.

  The semiconductor device 400 can automatically control the channel impedance of the variable impedance element 210 without adjustment from the outside, has a simple configuration, and contributes to miniaturization of the ECM.

  By using the semiconductor device of the present invention, it is possible to simultaneously improve the transient characteristics of the ECM and reduce the noise, thereby improving the performance of the ECM.

  The present invention mainly assumes a semiconductor device for a microphone, but the present invention is not necessarily limited to this, and only a capacitive element (capacitance component) is connected between a gate and a source. It can be widely applied to circuits.

  As described above, according to the present invention, the impedance value of the variable impedance can be changed according to the operation state of the JFET, and the semiconductor device capable of simultaneously improving the transient characteristics and the noise characteristics that were impossible in the past. Is realized.

  That is, the impedance of the variable impedance element is lowered at the beginning of power-on to improve the transient characteristics of the drain current. After the drain current is stabilized, the impedance of the variable impedance element is increased to improve the S / N ratio of the JFET. Can be realized.

  Also, by adopting a circuit configuration in which the variable impedance element is composed of a JFET or a depletion type MOSFET, and the gate of the JFET or depletion type MOSFET (depletion type FET) is connected to the drain of the main JFET. Thus, it is possible to automatically perform appropriate control of the impedance of the variable impedance element.

  That is, at the moment when the power is turned on, since the depletion type FET as the variable impedance element has a low impedance, an effect that the transient drain current can be quickly absorbed is obtained. When the drain voltage is stabilized, a voltage is applied to the depletion type FET, and the channel is closed to increase the impedance, so that an effect of suppressing noise of the JFET can be obtained. Since automatic adjustment of the variable impedance is possible, it is not necessary to supply a control signal from the outside, the circuit configuration is simplified, and therefore, the ECM or the like is not hindered in size reduction or thickness reduction.

  Further, by using a depletion type MOSFET as a variable impedance element, electrical insulation between the gates of each FET can be easily ensured. Also, in the case of MOSFET, unlike JFET, no gate current flows, so there is also an advantage that complete high resistance (resistance with infinite impedance) can be realized by controlling the gate voltage.

  In addition, by providing an independent gate terminal to the JFET or depletion type MOSFET as a variable impedance element, it is possible to freely control the impedance value, the timing of changing the impedance value, or the mode of the change. Thus, a more accurate design can be performed. For example, when a specific signal component is input from a microphone, the variable impedance element can be reduced in impedance so that the component is released so that no sound is collected by the microphone.

  Further, the ECM is widely used as a microphone for a portable terminal such as a cellular phone, and in recent years, its miniaturization, thinning, and high performance are strongly demanded. An ECM using the present invention can satisfy these requirements.

  Further, when a JFET or a depletion type MOSFET is used as a variable impedance element and integrated with an original JFET, it is not necessary to form a high resistance made of polysilicon on a semiconductor substrate as in the prior art. Therefore, the semiconductor device can be thinned.

  In recent years, with further reduction in size and weight of portable terminals, there is a strict demand for thinner ECM. The semiconductor device of the present invention contributes to thinning of the ECM.

  Further, the main JFET and the depletion type FET as the variable impedance element can be efficiently formed on the same semiconductor substrate by the semiconductor device manufacturing method of the present invention. In particular, by selectively introducing impurities, the main JFET and the depletion type FET as a variable impedance element can be simultaneously formed, and the number of processes can be reduced.

  At this time, by appropriately controlling the gate length (L) and the gate width (W) of the depletion type FET as the variable impedance element, the characteristics of the variable impedance element can be adjusted with high accuracy to obtain desired characteristics. Can be realized.

  INDUSTRIAL APPLICABILITY The present invention can be used for all semiconductor devices including JFETs whose capacitance is connected between the gate and the source, and is particularly useful for microphone semiconductor devices such as electret condenser microphones.

The circuit diagram which shows the basic circuit structure of the semiconductor device of this invention The circuit diagram which shows an example of the concrete circuit structure of the semiconductor device of this invention The circuit diagram which shows the other example of the concrete circuit structure of the semiconductor device of this invention Sectional drawing of a semiconductor device for demonstrating the 1st manufacturing process of the semiconductor device of this invention Sectional drawing of a semiconductor device for demonstrating the 2nd manufacturing process of the semiconductor device of this invention Sectional drawing of a semiconductor device for demonstrating the 3rd manufacturing process of the semiconductor device of this invention Sectional drawing of a semiconductor device for demonstrating the 4th manufacturing process of the semiconductor device of this invention Sectional drawing of the semiconductor device for demonstrating the surface electrode formation process in the 5th manufacturing process of the semiconductor device of this invention Sectional drawing of a semiconductor device for demonstrating the back surface electrode (main JFET gate electrode) formation process in the 5th manufacturing process of the semiconductor device of this invention The figure for demonstrating the mounting structure of the electret condenser microphone (ECM) carrying the semiconductor device of this invention. Circuit diagram showing general configuration of microphone JFET Circuit diagram showing equivalent circuit of electret condenser microphone (ECM)

Explanation of symbols

51 P ++ conductivity type substrate 52 P type epitaxial layer 53 (53a, 53b) N type channel layer 54 Channel isolation layer 55 JFET P type channel layer (variable impedance channel layer)
56 Oxide Film 57 Gate Diffusion Layer 58 Oxide Film 59 Main JFET Source Diffusion Layer 60 Main JFET Drain Diffusion Layer 61 (61a, 61b) JFET Gate Layer as Variable Impedance Element 62 Oxide Film 63 (63a-63e) Semiconductor Device 64 The gate electrode formed on the back surface of the semiconductor device 100 Main JFET (for example, N channel type JFET)
200 Variable impedance element 210, 220 FET (P-channel JFET or depletion type MOSFET) as a variable impedance element
230 Independent gate terminal as impedance control terminal

Claims (8)

A junction field effect transistor;
A semiconductor device having a variable impedance element connected between the gate and source of the junction field effect transistor. The semiconductor device according to claim 1,
The variable impedance element is a junction field effect transistor, a gate of the junction field effect transistor is connected to a drain of the junction field effect transistor, and two signal terminals of the junction field effect transistor are provided. A semiconductor device in which one terminal is connected to a gate of the junction field effect transistor and the other terminal is connected to a source of the junction field effect transistor. The semiconductor device according to claim 1,
The variable impedance element is a depletion type MOS field effect transistor, a gate of the depletion type MOS field effect transistor is connected to a drain of the junction type field effect transistor, and the depletion type MOS field effect transistor One of the two signal terminals of the junction type MOS field effect transistor is connected to the gate of the junction field effect transistor, and the other terminal is connected to the source of the junction type field effect transistor. Semiconductor device. The semiconductor device according to claim 1,
The said variable impedance element is a semiconductor device which is a junction field effect transistor provided with the gate terminal which can apply the control voltage for impedance adjustment from the outside, or the said depletion type MOS field effect transistor. A semiconductor device according to any one of claims 1 to 4,
A semiconductor device in which a capacitive element is connected between the gate and source of the junction field effect transistor. A semiconductor device according to any one of claims 1 to 4,
The semiconductor device constitutes a microphone, and an electret capacitor that functions as an acoustoelectric conversion element is connected between the gate and source of the junction field effect transistor.   An electret condenser microphone configured by housing the semiconductor device according to claim 6 and the electret condenser in the same casing. A method for manufacturing a semiconductor device in which a junction field effect transistor as a first transistor and a junction field effect transistor functioning as a variable impedance element as a second transistor are integrated on the same substrate,
Forming a second conductive type semiconductor layer (53) on a first conductive type semiconductor substrate (51, 52) functioning as a gate of the first transistor;
Impurities having the first conductivity type are introduced into the second conductivity type semiconductor layer (53), and the second conductivity type semiconductor layer (53) is formed in the formation regions of the first and second transistors. Forming a separation layer (54a, 54b, 54c) for separation, and simultaneously forming a channel diffusion layer (55) of the second transistor;
An impurity exhibiting the first conductivity type is selectively introduced into the formation region of the first transistor in the second conductivity type semiconductor layer (53) to function as a part of the gate of the junction field effect transistor. A third step of forming a diffusion region (57) of the first conductivity type;
An impurity having the second conductivity type is selectively introduced into each of the first and second transistor formation regions of the second conductivity type semiconductor layer (53), and the source layer (59 of the first transistor). And a drain layer (60), and at the same time, a fourth step of forming the gate layer (61a or 61b) of the second transistor as the variable impedance;
A fifth step of forming electrode layers (63a, 63b, 63c, 63d, 63e, 64);
A method for manufacturing a semiconductor device, comprising:

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