Oxide Semiconductor Transistor Edge Isolation
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Solution Overview
Problem
Transistors using oxide semiconductor films exhibit unstable electric characteristics due to impurity entry or oxygen release, particularly at the end portions, leading to the formation of parasitic channels, which affect threshold voltage and current drive capability.
Innovation Solution
A semiconductor device structure where at least one of the source or drain electrodes is positioned to avoid electrical connection with the end portion of the oxide semiconductor film, using a specific layer configuration and materials to prevent impurity entry and oxygen release, including a gate electrode layer with barrier layers and an oxide semiconductor film with aligned crystal parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source and drain electrodes are electrically connected to the end portion of the oxide semiconductor film, then the electrical connection is ensured, but a parasitic channel is formed at the end portion causing unstable electric characteristics
Solution Approach 1:
The patent extracts the harmful interaction between the source/drain electrodes and the end portion of the oxide semiconductor film by positioning the electrodes to overlap with the gate electrode layer rather than extending to the end portions, thereby eliminating the parasitic channel formation while maintaining necessary electrical connections
2Ease of manufacture
If the oxide semiconductor film is used for transistor channel, then the transistor can be formed, but impurity entry or oxygen release causes threshold voltage changes and electric characteristic instability
Solution Approach 1:
The patent applies local quality by creating different structural configurations in different regions: the source and drain electrodes are positioned to overlap with the gate electrode layer in the channel region, while avoiding contact with the end portions of the oxide semiconductor film, thereby providing different functional properties to different regions of the device
Data Source
AI summary
An object of one embodiment of the present invention is to provide a highly reliable semiconductor device by giving stable electric characteristics to a transistor including an oxide semiconductor film. The semiconductor device includes a gate electrode layer over a substrate, a gate insulating film over the gate electrode layer, an oxide semiconductor film over the gate insulating film, a drain electrode layer provided over the oxide semiconductor film to overlap with the gate electrode layer, and a source electrode layer provided to cover an outer edge portion of the oxide semiconductor film. The outer edge portion of the drain electrode layer is positioned on the inner side than the outer edge portion of the gate electrode layer.