Active solid-state devices (e.g. – transistors – solid-state diode – Schottky barrier – In integrated structure
Reexamination Certificate
2001-11-13
2003-06-03
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Schottky barrier
In integrated structure
C257S474000, C257S549000, C257S561000
Reexamination Certificate
active
06573582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device having characteristics suitable for forming a drive circuit for a power integrated circuit (hereinafter referred to as “power IC”).
2. Background Art
Some driver circuit of a power IC includes a bipolar transistor.
FIG. 1
is a sectional view of a semiconductor device including a bipolar transistor, for the driver circuit of a power IC and
FIG. 2
is a sectional view of assistance in explaining the operation of the semiconductor device shown in FIG.
1
.
Referring to
FIG. 1
, the semiconductor device has a p-type semiconductor substrate
10
. An n-type collector region
12
is formed in an upper part of the semiconductor substrate
10
. A p-type base region
14
is formed in the surface of the collector region
12
. An n-type emitter region
16
is formed in the surface of the base region
14
.
The collector region
12
, the base region
14
and the emitter region
16
constitute a bipolar transistor. A buried region
18
of a width slightly greater than that of the emitter region
16
is formed in the vicinity of the boundary between the semiconductor substrate
10
and the collector region
12
. The buried region
18
is a region of an n
+
-type semiconductor formed by diffusion. The buried layer
18
reduces the collector resistance of the bipolar transistor and suppresses the flow of leakage current from the bipolar transistor to the semiconductor substrate
10
.
The driver circuit of the power IC needs a transistor for supplying power to a circuit to be driven (hereinafter referred to as “driven circuit”), and a diode for discharging electric energy accumulated in an inductor component (hereinafter referred to as “inductor”) of the driven circuit. In the semiconductor device shown in
FIG. 1
, the joint of the semiconductor substrate
10
and the collector region
12
forms a diode
20
(hereinafter referred to as “collector/substrate diode
20
”). The semiconductor device shown in
FIG. 1
is suitable for forming the driver circuit of the power IC in a compact structure.
In
FIG. 2
, the semiconductor substrate
10
of the semiconductor device is grounded, and the collector region
12
is connected to an inductor
22
. The collector/substrate diode
20
permits a current to flow from the semiconductor substrate
10
into the inductor
22
, so that electric energy accumulated in the inductor
22
can be discharged.
Time necessary to discharge the electric energy accumulated in the inductor
22
is dependent on the operating speed of the collector/substrate diode
20
. It is desirable that the electrical energy can be discharged in a short time in view of suppressing of a power loss in the driver circuit; that is, it is desirable that the operating speed of the collector/substrate diode
20
is high. However, a structural restriction makes it difficult for the collector/substrate diode
20
to operate at a high operating speed. Consequently, the driver circuit employing the conventional semiconductor device is apt to involve a large power loss.
SUMMARY OF THE INVENTION
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a semiconductor device of construction suitable for forming a driver circuit.
According to one aspect of the present invention, a semiconductor device comprises a semiconductor substrate, a bipolar transistor formed on the semiconductor substrate and having a collector region, a Schottky diode formed in the collector region of the bipolar transistor, and a potential isolating layer isolating the collector region and the semiconductor substrate in potential from each other.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
REFERENCES:
patent: 4168997 (1979-09-01), Compton
patent: 4550491 (1985-11-01), Depey
patent: 4831430 (1989-05-01), Umeji
patent: 4936928 (1990-06-01), Shaw et al.
patent: 4982244 (1991-01-01), Kapoor
patent: 5828124 (1998-10-01), Villa
patent: 2056767 (1981-03-01), None
patent: 58-78451 (1983-05-01), None
patent: 3-14270 (1991-01-01), None
Terashima Tomohide
Yamamoto Fumitoshi
Yamashita Yasunori
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Nadav Ori
Thomas Tom
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