Semiconductor Device With Second Gate Electrode For Threshold Control
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Solution Overview
Problem
Complementary logic circuits experience increased power consumption and heat generation due to through currents, especially as integration density and driving frequency increase, as both p-channel and n-channel transistors are turned on during potential switching, leading to inefficiencies.
Innovation Solution
Incorporating a second gate electrode to control threshold voltage in transistors within the complementary logic circuit, combined with the use of an insulated gate field-effect transistor with extremely low off-state current and a highly purified oxide semiconductor material with a wider band gap and lower intrinsic carrier density, to manage and reduce through currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a complementary logic circuit uses conventional transistors without threshold voltage control, then the circuit structure is simple, but power consumption increases due to through current during potential switching
Solution Approach 1:
The gate electrode is divided into two independent parts: a first gate electrode for basic switching control and a second gate electrode for threshold voltage control. This segmentation allows independent optimization of switching operation and threshold adjustment, enabling through current reduction without complicating the overall circuit architecture.
Solution Approach 2:
The threshold voltage of the transistor is made dynamically adjustable through the second gate electrode, which can apply different potentials to shift the threshold voltage. This dynamic control allows the transistor to adapt its characteristics during operation, reducing through current by optimizing the turn-off characteristics at different operating points.
2Productivity
If integration degree of the integrated circuit is increased, then productivity improves, but power consumption due to through current increases significantly
Solution Approach 1:
The invention changes the electrical parameters of the transistor by introducing a second gate electrode that can adjust the threshold voltage. This parameter adjustment capability allows transistors in high-density integrated circuits to operate with optimized threshold voltages, reducing through current and thereby reducing the cumulative power consumption across billions of transistors in the integrated circuit.
3Productivity
If driving frequency is increased to GHz level, then productivity improves, but heat generation due to through current becomes large
Solution Approach 1:
The second gate electrode is used to preliminarily adjust the threshold voltage before the main switching operation occurs. By pre-setting the appropriate threshold voltage through the second gate, the transistor is prepared to minimize through current during subsequent high-frequency switching operations, thereby reducing heat generation even at GHz driving frequencies.
4Speed
If a transistor with higher mobility material is used, then speed improves, but off-state current increases leading to higher power consumption
Solution Approach 1:
The invention applies different control mechanisms to different aspects of transistor performance: the first gate electrode controls the main channel conduction for high-speed operation, while the second gate electrode independently controls the threshold voltage to suppress off-state current. This localized control of different transistor characteristics allows simultaneous optimization of both speed and off-state current.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces through currents, thereby minimizing power consumption and heat generation, while maintaining low off-state current densities and improving the reliability of the semiconductor device.
Implementation Method 1
a channel formation region which includes a semiconductor material whose band gap is wider than that of a silicon semiconductor and whose intrinsic carrier density is lower than that of silicon
Implementation Method 2
a channel formation region which includes a semiconductor material whose band gap is wider than that of a silicon semiconductor and whose intrinsic carrier density is lower than that of silicon
Implementation Method 3
The threshold voltage of the transistor having the second gate electrode is controlled by the height of the potential of the second gate electrode, more specifically by the potential difference between the source electrode and the second gate electrode
Implementation Method 4
an insulated gate field-effect transistor (hereinafter simply referred to as a transistor) with an extremely low off-state current is used as a switching element to control the potential of the second gate electrode
Data Source
AI summary
An n-channel transistor or a p-channel transistor provided with a second gate electrode for controlling a threshold voltage in addition to a normal gate electrode is used for a complementary logic circuit. In addition, an insulated gate field-effect transistor with an extremely low off-state current is used as a switching element to control the potential of the second gate electrode. A channel formation region of the transistor which functions as a switching element includes a semiconductor material whose band gap is wider than that of a silicon semiconductor and whose intrinsic carrier density is lower than that of silicon.