Inverter Circuit Driving Frequency via Dual-Gate Threshold Control
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Solution Overview
Problem
Inverter circuits with transistors of the same conductivity type suffer from reduced driving frequency and increased power consumption due to longer rise times and off-state leakage currents, limiting their performance in logic circuits.
Innovation Solution
The configuration of logic circuits using transistors with a second gate electrode to control threshold voltages individually, allowing for normally-on and normally-off characteristics, which enhances current drive capability and reduces leakage current, thereby increasing driving frequency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an inverter circuit is formed with all transistors having the same conductivity type, then the circuit can be fabricated using uniform transistor structures, but the driving frequency is lowered due to longer rise time of output signals
Solution Approach 1:
The gate electrode is divided into two separate gate electrodes (first gate electrode and second gate electrode) that can independently control the transistor. This segmentation allows one transistor to have normally-on characteristics (high driving capability) while another has normally-off characteristics, resolving the contradiction between uniform structure and high driving frequency
Solution Approach 2:
The threshold voltage of transistors is changed by applying different potentials to the two gate electrodes. By controlling the potential of the second gate electrode, the threshold voltage can be adjusted to achieve either normally-on or normally-off characteristics, enabling high-speed operation while maintaining manufacturing uniformity
2Device complexity
If an inverter circuit is formed with all transistors having the same conductivity type, then the circuit structure is simplified, but power consumption is increased due to off-state leakage current
Solution Approach 1:
The transistor characteristics are made dynamically adjustable through the second gate electrode. The transistor can switch between normally-on and normally-off states by changing the potential applied to the second gate electrode, allowing the circuit to optimize power consumption while maintaining structural simplicity
Solution Approach 2:
By changing the threshold voltage parameter through potential control of the second gate electrode, the transistor can be configured to have normally-off characteristics that minimize off-state leakage current, thereby reducing power consumption without increasing circuit complexity
3Adaptability or versatility
If one transistor serves as current source and another as switch in the inverter circuit, then the circuit can operate with same conductivity type transistors, but the rise time of output signal becomes longer
Solution Approach 1:
The gate control is segmented into two independent electrodes, allowing the transistor assigned as current source to have enhanced driving capability through appropriate potential application to the second gate electrode, thereby reducing rise time while maintaining the versatility of role assignment
Data Source
AI summary
To provide a semiconductor device including an inverter circuit whose driving frequency is increased by control of the threshold voltage of a transistor or a semiconductor device including an inveter circuit with low power consumption. An inverter circuit includes a first transistor and a second transistor each including a semiconductor film in which a channel is formed, a pair of gate electrodes between which the semiconductor film is placed, and source and drain electrodes in contact with the semiconductor film. Controlling potentials applied to the pair of gate electrodes makes the first transistor have normally-on characteristics and the second transistor have normally-off characteristics. Thus, the driving frequency of the inverter circuit is increased.