JPS5843579A - Variable capacity element - Google Patents

Abstract

PURPOSE:To obtain a variable capacity element so constituted that the bias terminal for depletion layer control and the terminal for capacity reading are independent in a DC meaning. CONSTITUTION:The first electrode 9 constituted of an ohmic electrode and the second electrode 10 constituted of an MOS structure via an insulating film 11 are respectively provided on one side semiconductor layer forming a P-N junction part 3 resulting in a constitution so as to use said first electrode as the bias terminal for depletion layer control and the second electrode as the terminal 12 for capacity reading. The width D of a depletion layer 8 expanding to both sides of the P-N junction part is varied by varying the bias voltage 6 for said depletion layer control. Thus, the variation of capacity values with the variation of the width D of said depletion layer 8 is read out from the terminal part 12 for capacity reading. In this case, since said electrode 10, insulating film 11 and N type semiconductor layer 2 constitute what is called an MOS structure, a series capacity wherein a capacity due to the insulating film 11 itself and one due to the P type semiconductor layer 1 and an N type semiconductor layer 2 are added in series to a capacity due to the rate of variation of the depletion layer 8 is read out from said terminal 12 for capacity reading.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable capacitance element configured such that a bias terminal for controlling a depletion layer and a terminal for extending a capacitance are independent in terms of direct current.

A PN junction diode as shown in FIG. 1 has been conventionally used as a variable capacitance element.

In the figure, 'C1 is an N-type semiconductor layer; 2 is a P-type layer that is in contact with this N-type layer l and forms a PN junction 3; 4.5 is the above-mentioned N-type semiconductor layer;
Ohmic electrodes provided on the type layer 1 and the P-type layer 2, 6 are for depletion layer control connected between 1 and mic electrodes 4.5 to provide a reverse bias (Iasmium pressure, 7 is the capacitance) This is the terminal part for continuous output.

In the above configuration, the depletion layer 8 spreads on both sides of the PN junction 3 (mainly toward the side with lower impurity concentration) by varying the depletion layer control insulator pressure 6'. Since the width changes, the change in capacitance value based on this change is read out from the capacitance successive output terminal section 7.

However, since the conventional variable capacitance element described above is a two-terminal element, the bias terminal for controlling the depletion layer and the terminal for increasing the capacitance are constituted by a common electrode and are not independent in terms of direct current. When applied to a device, the input signal may cause unnecessary capacitance changes, etc., which may cause tuning errors.

Therefore, there was a drawback that the applications were restricted.

The present invention has been made to eliminate the above-mentioned drawbacks.
N! While forming a joint joint, a first electrode and a second electrode are provided on each of the semiconductor layers via an insulating film, and the first electrode serves as a depletion layer control terminal and the second electrode 5 serves as a capacitor. The present invention provides a variable capacitance element configured so that the two terminals are independent in terms of direct current by being used as a terminal for the purpose of the present invention. Book i, with reference to the drawings below! Example A will be explained. Figure 1 is a cross-sectional view showing a variable capacitance element according to an embodiment of the present invention, and the same parts as in Figure 1 are designated by the same numbers, and 9 is a P
The ohmic electrode 10 provided on the P-type semiconductor layer 2 is an electrode provided on the P-type semiconductor layer 2 via an insulating film 1, for example, a silicon oxide film, and is a terminal portion for continuous output of a 12-porous capacitance.

In the above structure, 7. The bias voltage for controlling the depletion layer 6
By varying this, the width of the depletion layer 8 extending on both sides of each PN contact portion can be varied. From this, a change in capacitance value is read out according to a change in the width of the depletion layer above the capacitance reading terminal section ``'' or ff. 11 and the N-type semiconductor layer 2 constitute a so-called MO8 structure, so that from the capacitance reading terminal 12, there is a capacitance of 4 due to the change in the depletion layer 8, a capacitance due to the insulating film 1] itself, and a P-type semiconductor. layer 1
．． The capacitance due to the N-type semiconductor layer 2 is added in series, and the series capacitance is calculated.

As the insulating film 11, a silicon oxide film is taken as an example, but any dielectric material can be used.

Furthermore, each semiconductor layer can be made of any semiconductor material including silicon, and the conductivity type of each semiconductor layer can even be arbitrarily selected.

As is clear from the above description, according to the present invention, the ohmic electrode 7 is formed on the semiconductor layer on one side forming the PN junction. - A second electrode of MO8 structure is provided through the electrode and the edge film, respectively. Since the first electrode is configured to be used as a terminal for connecting air, the depletion layer side is The bias terminal and the capacitance readout terminal can be made independent in terms of direct current. - Therefore, even when applied to a tuned circuit, etc., there will be no tuning deviation due to the influence of the input signal, so it can be applied to a wide range of applications. I will be able to do it.

In particular, by providing a continuous capacitive electrode via an insulating film as in the present invention, the leakage current can be suppressed to a low level, so higher performance operation can be expected.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are sectional views showing a conventional example and an embodiment of the present invention, respectively. 2-3...PN junction,
6... Insulator pressure for controlling depletion layer, 8... Depletion layer, 9... Ohmic electrode (empty, depletion, layer control (A, 1 as electrode), 10... Capacity Readout electrode 1.111・
...Insulating film, 12...Capacitance reading terminal.・Patent applicant: Clarion Co., Ltd. 1st decoy 2nd prisoner

Claims (1)

[Claims] 1. a first conductivity type semiconductor layer; A second conductive type semiconductor layer that forms a part of a PN junction in contact with the first conductive type semiconductor layer, and an insulating film on the first electrode provided on the second conductive type semiconductor layer and the second conductive type semiconductor layer. the second provided through
1. A variable capacitance element comprising: an electrode, the first electrode being used as an i2 layer control bias terminal, and the second electrode being used as a capacitance successive terminal. 2. The variable capacitance element according to claim 1, wherein the insulating film is made of a silicon oxide film.