TFET Threshold Voltage Regulation via Separate Electrode
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Solution Overview
Problem
Tunnel field effect transistors (TFETs) face significant variations in off current due to their steep sub-threshold swing, which cannot be regulated like MOSFETs, as they lack a substrate electrode, making it impossible to adjust the threshold voltage post-device completion.
Innovation Solution
Incorporating a threshold regulating electrode on a semiconductor device, separate from the gate electrode, allows for the regulation of the threshold voltage by applying different potentials, thereby controlling the tunneling barrier and current flow between the source and drain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TFET is designed with a steep sub-threshold swing to achieve high on current and low off current, then the on/off current ratio is improved, but the variations in off current increase and the threshold voltage cannot be regulated
Solution Approach 1:
The invention divides the control function into two separate electrodes: a gate electrode for primary control and a threshold regulating electrode for threshold voltage adjustment. This segmentation allows independent optimization of on/off ratio and threshold voltage regulation without interference between functions.
Solution Approach 2:
The threshold regulating electrode acts as an intermediary element that mediates between the gate electrode and the channel, enabling threshold voltage regulation through its potential. This intermediary structure allows the TFET to achieve MOSFET-like threshold voltage control while maintaining the steep sub-threshold swing characteristic.
2Reliability
If the TFET is constituted on a bulk substrate with asymmetric diffusion layer, then the steep sub-threshold swing is achieved, but the substrate electrode cannot be added for threshold voltage regulation
Solution Approach 1:
The invention adds a new dimension to the device structure by introducing a threshold regulating electrode in a different spatial dimension (above the gate electrode). This dimensional addition enables threshold voltage regulation functionality without modifying the bulk substrate or asymmetric diffusion layer structure that provides the steep sub-threshold swing.
3Ease of manufacture
If the threshold voltage is determined by gate insulating film thickness or junction abruptness, then the device structure is simple, but the threshold voltage cannot be adjusted after device completion
Solution Approach 1:
The invention transforms the static threshold voltage (determined during manufacturing by gate insulating film thickness or junction abruptness) into a dynamic parameter that can be adjusted after device completion. The threshold regulating electrode enables post-manufacturing threshold voltage tuning by applying different potentials, making the device adaptable to different applications.
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 approach enables precise control over the threshold voltage of TFETs, reducing off current variations and enhancing the on/off current ratio, similar to MOSFETs, by modifying the potential applied to the threshold regulating electrode.
Implementation Method 1
a tunnel field effect transistor (TFET) is an LSI-applicable, low-power consumption transistor having different type between a source and a drain of a semiconductor, and an asymmetric diffusion layer. Since a sub-threshold swing (hereinafter, referred to as SS) steeper than that of a MOSFET can be obtained, TFET can realize a high on current and a low off current.
Data Source
AI summary
In one embodiment, a semiconductor device includes a first diffusion layer of a first conductivity type and a second diffusion layer of a second conductivity type that are provided in a semiconductor layer at a distance, the second conductivity type being an opposite conductivity type of the first conductivity type, a first insulating film and a second insulating film that are provided on the semiconductor layer between the first diffusion layer and the second diffusion layer at a distance, a gate electrode provided on the first insulating film, and a threshold regulating electrode provided on the second insulating film.