Field-Effect Transistor Miniaturization via Electrode Thickness
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Solution Overview
Problem
The existing structure of field-effect transistors is not suitable for miniaturization due to variations in contact hole positions and the requirement of an impurity region between the channel and low resistance regions.
Innovation Solution
A field-effect transistor design with a semiconductor film, a gate insulating film, and source and drain electrodes where the thickness of the source and drain electrodes is less than the gate insulating film, and the gate insulating film has a region not in contact with the electrodes, allowing for miniaturization by eliminating the need for contact holes and impurity regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If contact holes and impurity regions are used in the conventional structure, then the transistor can be produced with standard manufacturing processes, but the transistor size cannot be miniaturized
Solution Approach 1:
The invention extracts and eliminates the contact holes and impurity regions from the conventional transistor structure. By forming the source and drain electrodes to directly contact the semiconductor film without requiring contact holes through the gate insulating film, and without requiring impurity regions between the channel and low resistance regions, the structure is simplified and miniaturization is enabled while maintaining manufacturability
Solution Approach 2:
The invention changes the dimensional relationship between the source/drain electrodes and the gate insulating film. Instead of the electrodes being thicker than or equal to the gate insulating film (requiring contact holes), the electrodes are made thinner than the gate insulating film, allowing direct contact with the semiconductor film in a different dimensional configuration that eliminates the need for contact holes and impurity regions
2Speed
If the gate insulating film is made thin to reduce capacitance, then the transistor speed improves, but the source and drain electrodes may contact the gate electrode causing leakage current
Solution Approach 1:
The invention creates an asymmetric thickness relationship where the source and drain electrodes are deliberately made thinner than the gate insulating film. This asymmetric design ensures that even when the gate insulating film is thin (for high speed), the electrodes cannot penetrate through to contact the gate electrode, thus preventing leakage current while maintaining fast transistor operation
Solution Approach 2:
The invention applies preliminary anti-action by designing the electrode thickness to be less than the gate insulating film thickness before any contact could occur. This pre-established dimensional relationship prevents the harmful effect of electrode-to-gate contact and leakage current from happening in the first place, allowing the gate insulating film to be made thin for high speed operation without compromising reliability
Data Source
AI summary
(Object) To miniaturize a field-effect transistor. (Means of Achieving the Object) A field-effect transistor includes a semiconductor film formed on a base, a gate insulating film formed on a part of the semiconductor film, a gate electrode formed on the gate insulating film, and a source electrode and a drain electrode formed in contact with the semiconductor film, wherein a thickness of the source electrode and the drain electrode is smaller than a thickness of the gate insulating film, and the gate insulating film includes a region that is not in contact with the source electrode or the drain electrode.