Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2002-02-12
2003-12-16
Fahmy, Wael (Department: 2814)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S149000
Reexamination Certificate
active
06664148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an integrated circuit that can be switched between an active mode and standby a mode, and more particularly to an integrated circuit having two processing circuits that are supplied in common by a power-supply voltage.
2. Description of the Related Art
Integrated circuit devices having a plurality of processing circuits are now being manufactured as one-chip microcomputers and are being employed in electronic apparatus such as portable telephones.
An electronic apparatus such as a portable telephone that is carried by a user inevitably takes a battery as its power supply, and batteries are therefore being made lighter and more compact to meet the demand for smaller and lighter devices. However, the additional demand for long operating time results in a drastic need for reduction in the power consumption of these integrated circuit devices. In the case of digital portable telephones, moreover, these integrated circuit devices must also be capable of high-speed operation in order to carry out digital processing of speech signals in real time.
Although waiting for incoming calls necessitates constant operation in the case of a portable telephone, not all components need operate constant. Integrated circuit devices in current portable telephones realize lower power consumption by operating only the minimum necessary processing circuits during standby.
Further, the drive voltage of the transistors of processing circuits may also be increased to accelerate the operation of an integrated circuit device. Merely increasing the drive voltage, however, inevitably increases power consumption, while decreasing the drive voltage lowers the operating speed of transistors, but both decreasing the drive voltage and reducing the thickness of the gate insulation film of transistors can increase ON current and realize high-speed operation while reducing the power consumption.
Reducing the thickness of the gate insulation film of a transistor, however, results in an increase in gate leak current even if the drive voltage is reduced to prevent variation in operating speed. As shown in
FIG. 1
, if the gate insulation film thickness of a transistor is 20 Å, its gate length is 0.1 &mgr;m and its gate width is 10 &mgr;m, for example, a gate leak current of 10 pA occurs between the gate electrode and semiconductor substrate even with a drive voltage of 1.2 V.
In a CMOS (Complementary Metal Oxide Semiconductor) circuit in particular, drive voltage is constantly applied between one of gate electrodes of the n-type and p-type MOS transistors and the semiconductor substrate, with the result that a gate leak current is constantly generated. Integrated circuit devices currently may integrate several million transistors, and the gate leak current therefore cannot be ignored. In an integrated circuit device having five million CMOS transistors, for example, the total gate leak current reaches a maximum of 25 &mgr;Å.
The gate leak current of the transistors therefore increases despite both reducing the power-supply voltage and decreasing the thickness of the gate insulation film of the integrated circuit device so as to realize high-speed operation while reducing power consumption during operation as described hereinabove. As a result, satisfactory reduction of power consumption during standby is problematic. Increasing the thickness of the gate insulation film of the transistors of the integrated circuit device can reduce the gate leak current of the transistors, but this increase in layer thickness complicates high-speed operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an integrated circuit device that is capable of high-speed operation at a low current during operation while reducing power consumption during standby.
It is another object of the present invention to provide an electronic apparatus that includes the above-described integrated circuit device.
It is a further object of the present invention to provide a method of fabricating the above-described integrated circuit device.
According to one aspect of the present invention, an integrated circuit device comprises: means for switching each mode, means for generating a power-supply voltage, a first processing circuit having a first transistor, and a second processing circuit having a second transistor.
The first transistor has the thinnest gate insulation film and is driven by the power-supply voltage only during active mode. The second transistor has a gate insulation film that is thicker than the gate insulation film of the first transistor, and is driven by the power-supply voltage both during active mode and standby mode.
Although the second transistor operates at slower speed because its gate insulation film is not the thinnest, it can be driven in standby mode with minimal gate leak current. Since its gate insulation film is thinnest, the first transistor has greater gate leak current but can be driven to operate at high speed only during active mode.
The integrated circuit device executes processing that requires high-speed operation by high-speed transistors and executes processing that does not require high-speed operation by transistors having minimal leak current and therefore is capable of comprehensively realizing high-speed operation while reducing leak currents and can realize both higher performance and lower power consumption.
In an embodiment, an integrated circuit device further comprises a third processing circuit having a third transistor. The third transistor has a gate insulation film that is thicker than the gate insulation film of the second transistor and is driven at a higher voltage than the first and second transistors.
The third transistor has a high drive voltage and operates at high speed with little gate leak current because its gate insulation film is thickest. The first transistor has a low drive voltage, and although it has significant gate leak current because its gate insulation film is thinnest, it operates at high speed only during active mode. The second transistor does not have the thinnest gate insulation film and is driven by a low voltage and therefore can also operate in standby mode at a lower speed than the first transistor with minimal gate leak current.
The integrated circuit device executes processing requiring high-speed operation by high-speed transistors and executes processing that does not require high-speed operation by transistors having minimal leak current, and therefore is capable of comprehensively realizing high-speed operation while reducing leak currents and can provide both higher performance and lower power consumption.
In an embodiment, the second processing circuit turns the first processing circuit ON and OFF. In this case, a first processing circuit that is capable of high-speed operation but which is prone to significant gate leak current during standby can be turned ON and OFF by a second processing circuit that has slow operation but minimal gate leak current.
In an embodiment, the second processing circuit begins supplying voltage to the first processing circuit upon detecting the input of a prescribed signal from the outside during standby mode. In this case, the first processing circuit in standby mode can be activated by the input of a prescribed signal from the outside.
In an embodiment, the gate insulation film of the first transistor is composed of a thermal oxidation film that has been grown on the surface of a semiconductor substrate, and the gate insulation film of the second transistor is composed of a thermal oxidation film that has been grown, simultaneously with the gate insulation film of the first transistor, on the surface of a semiconductor substrate in which at least one of argon, fluorine, and a fluorine compound has been implanted.
In this case, the thermal oxidation film that is grown on the surface of a semiconductor substrate in which at least one of argon, fluorine, and a fluorine compound has been implanted is thicker
Goto Yoshiro
Imai Kiyotaka
Kimizuka Naohiko
Fahmy Wael
Trinh Hoa B.
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