Semiconductor Device Back Gate Potential Control
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Solution Overview
Problem
In semiconductor devices, the potential applied to the back gate of a transistor is not constant due to the need for external control, leading to insufficient data retention characteristics.
Innovation Solution
A semiconductor device configuration comprising a first circuit, a second circuit, a battery, a voltage generation circuit, and a switch, where the voltage generation circuit generates a potential lower than the battery potential to maintain a constant back gate potential, using power gating to control the transistor's state and charge retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external control is used to apply potential to the back gate, then the transistor can be controlled, but the potential becomes non-constant leading to insufficient data retention characteristics
Solution Approach 1:
The back gate potential is generated self-sufficiently within the transistor structure using the source potential and a diode-connected transistor, eliminating the need for external control circuits. This self-generated potential remains constant even when power supply voltage stops, providing excellent data retention characteristics without requiring periodic external adjustment.
Solution Approach 2:
A diode-connected transistor is introduced as an intermediary element between the source and the back gate. This intermediary transistor automatically establishes a stable potential relationship, ensuring the back gate potential remains constant through its inherent diode connection characteristics, thereby resolving the instability caused by external control methods.
2Loss of energy
If power supply voltage is stopped to save energy, then power consumption is reduced, but data retention becomes insufficient without constant back gate potential
Solution Approach 1:
The back gate potential generation circuit operates autonomously using the source potential, requiring no additional power supply. When the main power supply voltage stops, the circuit continues to maintain the back gate potential through the diode-connected transistor's inherent characteristics, ensuring data retention without consuming additional energy.
Solution Approach 2:
The diode-connected transistor is pre-configured to automatically maintain the back gate potential relationship. This preliminary structural arrangement ensures that when power supply stops, the potential relationship is already established and maintained without requiring any active control or additional power, thus preserving data retention characteristics.
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
This configuration ensures excellent data retention characteristics by maintaining a constant back gate potential and high threshold voltage, enhancing the device's ability to retain data even when power supply voltage is stopped.
Implementation Method 1
The battery comprises a first terminal and a second terminal. The first terminal of the battery is electrically connected to a wiring through which the second potential is applied. A potential of the first terminal of the battery is higher than a potential of the second terminal.
Implementation Method 2
The voltage generation circuit has a function of generating a third potential lower than the second potential. The second gate of the first transistor is electrically connected to the second terminal of the battery. The third potential is applied to the second gate and the second terminal of the battery.
Data Source
AI summary
A semiconductor device having excellent data retention characteristics. A transistor with a low off-state current is utilized to save and retain data stored in a memory circuit, and a potential to be applied to a back gate of the transistor is applied from a battery provided for each memory circuit. The potential applied to the back gate of the transistor and a potential for charging the battery are generated in a voltage generation circuit. The battery is charged utilizing power gating of the memory circuit and data retention characteristics is improved.