Dual Work Function Multi-Gate MOSFET for Channel Length Modulation
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Solution Overview
Problem
Channel length modulation issues arise when downscaling CMOS analog devices, requiring effective solutions to maintain performance and efficiency.
Innovation Solution
A multi-gate oxide dual work function (DWF)-MOSFET configuration is employed, featuring two gate electrodes with different work functions and insulator films, where the second gate electrode has a higher work function and thinner equivalent oxide thickness than the first, to enhance channel controllability and current driving capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channel length is downscaled to improve device density and integration, then device integration is improved, but channel length modulation occurs causing performance degradation
Solution Approach 1:
The gate structure is segmented into two distinct gate electrodes (first gate electrode and second gate electrode) with different work functions positioned at different locations along the channel. This segmentation allows independent control of threshold voltage and channel current, effectively suppressing channel length modulation while maintaining downscaled channel dimensions for high device integration
Solution Approach 2:
Different regions of the gate structure are assigned different work function values - the first gate electrode has a lower work function while the second gate electrode has a higher work function. This local quality differentiation enables precise control over electron injection and channel characteristics, preventing channel length modulation effects in downscaled devices
2Productivity
If threshold voltage is lowered to improve current driving capability, then electron injection is enhanced, but control over channel current becomes difficult
Solution Approach 1:
The gate is divided into two electrodes with different work functions positioned at different channel locations. The first gate electrode with lower work function enhances electron injection and lowers threshold voltage, while the second gate electrode with higher work function provides control over channel current, achieving both improved current driving capability and maintainable control
Solution Approach 2:
The work function parameter is changed at different locations along the gate channel - using a lower work function material for the first gate electrode to enhance electron injection and a higher work function material for the second gate electrode to control channel current, thus achieving both low threshold voltage and controllable channel current
Data Source
AI summary
According to one embodiment, a semiconductor device includes a drain region, a source region, a channel region, a first gate insulator film provided on the channel region, a second gate insulator film provided on the channel region to be adjacent to the first gate insulator film on the source region side of the first gate insulator film, a first gate electrode provided on the first gate insulator film, and a second gate electrode provided on the second gate insulator film. An electrical thickness of the second gate insulator film is less than an electrical thickness of the first gate insulator film. A portion of the first gate electrode is provided on the second gate insulator film. A work function of the second gate electrode is higher than a work function of the first gate electrode.