Active solid-state devices (e.g. – transistors – solid-state diode – Regenerative type switching device – Device protection
Reexamination Certificate
2002-04-30
2003-07-15
Nelms, David (Department: 2818)
Active solid-state devices (e.g., transistors, solid-state diode
Regenerative type switching device
Device protection
C257S355000, C257S500000, C257S547000
Reexamination Certificate
active
06593601
ABSTRACT:
This application is based on an application No. 2001-138155 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated circuit device, and especially relates to inter-device isolation.
2. Related Art
FIGS. 1A and 1B
are schematic representations of an integrated circuit device which is a related art of the present invention.
FIG. 1A
is a plan view, whereas
FIG. 1B
is a sectional view. This integrated circuit device is roughly made up of a semiconductor substrate
901
, a first circuit
907
, a second circuit
908
, and connector terminals
906
. The semiconductor substrate
901
is formed from Si. The first circuit
907
includes semiconductor devices formed in the semiconductor substrate
901
and an insulator film and wires formed on the semiconductor substrate
901
(not illustrated). The second circuit
908
is provided at a different location from the first circuit
907
. The connector terminals
906
perform signal input/output with outside the integrated circuit device.
Also, an isolation region
902
is provided around the first circuit
907
, to prevent a signal from leaking between the first circuit
907
and the second circuit
908
through the semiconductor substrate
901
which has conductivity.
This isolation region
902
is formed by etching a trench in the semiconductor substrate
901
and filling the trench with an insulator such as silicon dioxide. In this way, a part of the semiconductor substrate
901
which belongs to the first circuit
907
and a part of the semiconductor substrate
901
which belongs to the second circuit
908
are isolated from each other.
However, the isolation region
902
, provided between the part of the semiconductor substrate
901
which belongs to the first circuit
907
and the part of the semiconductor substrate
901
which belongs to the second circuit
908
, forms the electrical equivalent of a capacitor. Hence the isolation region
902
cannot sufficiently suppress signal interference in a high-frequency range.
FIG. 2
shows an equivalent circuit of the integrated circuit device shown in
FIGS. 1A and 1B
. The principle of signal interference is explained below, by referring to FIG.
2
.
Each of the wires and semiconductor devices (not illustrated) included in the first and second circuits
907
and
908
is coupled to the semiconductor substrate
901
, through the capacitance of the insulator film (not illustrated) typically formed between the wire and the semiconductor substrate
901
and the junction capacitance between the semiconductor device and the semiconductor substrate
901
. These can be represented by capacitances
920
, a part
921
a
of the semiconductor substrate
901
which belongs to the first circuit
907
, and a part
921
b
of the semiconductor substrate
901
which belongs to the second circuit
908
.
The part
921
a
and the part
921
b
are opposed to each other with the isolation region
902
interposed in between. This isolation region
902
is made up of the insulator embedded in the trench. Accordingly, it can be said that the part
921
a
and the part
921
b
are connected to each other via an isolation capacitance
922
. A signal having a high-frequency component passes through the isolation capacitance
922
, so that interference occurs between the first circuit
907
and the second circuit
908
due to the signal leakage. This reduces the performance of the integrated circuit device. For example, if a noise signal having a high-frequency component is caused by a high-amplitude signal generated from a logic circuit or a local oscillator and leaks to another circuit that handles weaker signals, such as a radio signal receiving circuit, the performance of the receiving circuit may be markedly reduced. In particular, in the case of a direct conversion architecture which has been under study in recent years, a high-frequency oscillator needs to be used. This makes it impossible to ignore the effects of noise generated from such an oscillator. Thus, there are difficulties in integrating all necessary functions of a radio transmission/reception device, including receivers, logic circuits, and local oscillators, into a single integrated circuit device.
SUMMARY OF THE INVENTION
The present invention has an object of providing an integrated circuit device that can suppress undesired effects caused by leakage of noise signals between a plurality of circuits.
The stated object can be achieved by an integrated circuit device including: a first circuit which is formed on a semiconductor substrate; a second circuit which is formed on the semiconductor substrate at a location different from the first circuit; an isolation region which has a higher conductivity than the semiconductor substrate, and is formed in the semiconductor substrate between the first circuit and the second circuit; and a low impedance voltage output circuit which provides a fixed voltage at a low impedance, to the isolation region.
With this construction, even when a noise signal having a high-frequency component occurs, a current caused by the noise signal flows through the isolation region into the low impedance voltage output circuit, so that signal leakage between the first and second circuits is suppressed. This enables different circuits, such as logic circuits and transmission/reception circuits, which handle largely different levels of signals, to be integrated into a single integrated circuit device.
REFERENCES:
patent: 4628343 (1986-12-01), Komatsu
patent: 5545917 (1996-08-01), Peppiette et al.
patent: 5670799 (1997-09-01), Croft
patent: 6355537 (2002-03-01), Seefeldt
Fukuda Takeshi
Itoh Junji
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