JPS63274202A - Field effect transistor - Google Patents

Abstract

PURPOSE:To eliminate the variance in the matching characteristic by forming a matching circuit comprising a low pass filter between each electrode and an insulation layer so as to eliminate the need for a metallic thin wire between a matching capacitor and a substrate for matching. CONSTITUTION:A source lead-out electrode 4 formed onto a substrate, an insulation layer 5 coated onto the electrode 4, a gate lead-out electrode 2 on the insulation layer 5, a drain lead-out electrode 3 and a connection conductor 6 connecting the electrode 3 and a gate 1 of a function part are provided. Then a matching circuit comprising a low pass filter is formed between the electrodes and the insulation layer 6. That is, the matching circuit comprising the low pass filter consisting of the inductance by the external lead metallic thin wire and the capacitance formed through the insulation film 5 is formed. Thus, even with the variance in the external leads, the overall impedance is made close to the characteristic impedance of an external circuit by means of the matching circuit in the inside of the component at a prescribed size.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a field effect transistor (hereinafter abbreviated as FET), and in particular to a field effect transistor (FET) used in a high frequency region of
The present invention relates to the structure of an FET using aAs.

[Conventional technology]

Generally, when configuring an amplifier using FETs, a common source type is used because it is stable and easy to widen the band. As the number of elements in this amplifier that are operated in parallel increases, such as in a power amplifier, its input/output impedance decreases, making it difficult to match the characteristic impedance of the external line. Therefore, a matching circuit is installed near the elements. This facilitates matching outside the semiconductor device.

FIG. 6 shows a plan view of an example of a semiconductor device with an internal matching circuit using a conventional GaAs FET. As shown in the figure, since the input/output impedance of the semiconductor element 8 is lower than the external characteristic impedance, the semiconductor element 8 is provided between the matching substrate 10 via the internal matching capacitor 9 for impedance matching. These are connected to each other by thin metal wires 11.

This internal matching capacitor 9 operates as a low-pass filter.

[Problem that the invention seeks to solve]

In the conventional semiconductor device with a matching circuit described above, the matching circuit (
9) f! : Since the connection is made using thin metal wires 11, the characteristics of the matching circuit vary due to variations in the length of the thin metal wires 11, etc., and there is a drawback that it is difficult to obtain sufficient characteristics.

An object of the present invention is to eliminate such drawbacks, provide a field-effect transistor in which a matching circuit is provided within the element, eliminate thin metal wires, eliminate variations in matching characteristics, and facilitate connection with an external circuit. There is a particular thing.

[Means for solving problems]

The field effect transistor of the present invention has a structure including a source lead electrode formed on a substrate, an insulating layer deposited on the source lead electrode, and a gate lead electrode, a drain lead electrode, or a drain lead electrode formed on the insulating layer. A connection conductor portion that connects the gate/drain electrodes formed apart from each other and the gate/drain lead electrode, or the gate/drain electrode, the gate/drain lead electrode, or the gate/drain electrode and the functional part. A matching circuit including a low-pass filter is formed between each of the electrodes and the insulating layer.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

1(a) and 1(b) are a plan view of an embodiment of the present invention and a cross-sectional view of a fir tree taken along line A-A'.
2 is a gate function part, 2 is a gate extraction electrode, 3 is a drain extraction electrode, 4 is a source extraction electrode, 5 is an insulating film, 6 is a connecting conductor that connects the gate function part 1 and the gate extraction electrode 2, and 7 is a GaAs substrate. shows.

The equivalent circuit when using this FET with a common source is:
It will look like Figure 2. That is, the inductance L, ~
L3 is a thin metal wire for external extraction, and inside the broken line is the conductor part 6 according to the present invention and the source electrode 4-
A capacitor C1 formed of an insulator 5 inserted between gate electrodes 2 is shown. In this case, the impedance when looking from the gate conductor section 1 to the functional section side is that of the additional capacitor C1.
It is possible to achieve consistency by FIG. 3 is a Smith diagram showing this state, and shows a state in which a conductor part B and an additional capacitor C are provided to the functional part impedance A.

With this configuration, even if there are variations in the external lead, the matching circuit formed with a predetermined size inside the element will match the characteristic impedance of the external circuit close to the characteristic impedance of the external circuit, so the influence of the external circuit will be reduced. .

FIG. 4 is a plan view of a second embodiment of the present invention, and FIG. 5 is an equivalent circuit diagram of FIG. In this example, the insulation [1
The drain extraction electrode 3' is also connected to the source electrode (4) through 5.
It is placed above. In this case as well, since a matching circuit is provided within the element, there is little influence from external circuits, and connection with external circuits can be made easily.

〔Effect of the invention〕

As explained above, the present invention forms a matching circuit using inductance and capacitance formed near the element via an insulating film. This has the effect that it is possible to configure a circuit that is less affected by external circuits.

[Brief explanation of drawings]

Figure 1 (a>, (b) is a plan view and longitudinal cross-sectional view of an FET according to an embodiment of the present invention, Figure 2 is an equivalent circuit diagram of Figure 1, and Figure 3 is the input side of Figure 1. Smith diagram showing the state of
5 is a plan view of a second embodiment of the present invention, FIG. 5 is an equivalent circuit diagram of FIG. 4, and FIG. 6 is a plan view of an example of a conventional FET. 1... Functional part gate, 2... Gate extraction electrode, 3
．． 3'...Drain extraction electrode, 4...Source extraction electrode, 5...Insulator, 6...Connection conductor, 7...
GaAs substrate, 8... Semiconductor element, 9... Matching capacitor, 10... Matching substrate, 11... Metal thin wire. ,−゛

Claims (2)

[Claims] (1) A source extraction electrode formed on a substrate, an insulating layer deposited on this source extraction electrode, and a gate extraction electrode, a drain extraction electrode, or a gate formed separately on this insulating layer.・Equipped with a drain electrode, an extraction electrode of the gate/drain, or a gate/drain electrode, a connection conductor portion connecting the extraction electrode of the gate/drain, or the gate/drain electrode, and the functional part; A field effect transistor characterized in that a matching circuit including a low-pass filter is formed between the insulating layer and the insulating layer. (2) The field effect transistor according to claim 1, wherein the length of the connecting conductor is such that the imaginary part of the impedance when looking at the functional part from the end of the conductor exhibits inductivity in the operating frequency band.