Stepped Substrate Transistor Layout to Reduce Punch-Through
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Solution Overview
Problem
The miniaturization of semiconductor devices leads to increased likelihood of punch-through in transistors due to the proximity of the drain and source regions when high voltage is applied.
Innovation Solution
The semiconductor device is fabricated with a substrate featuring a first step structure with a first and second step portion, where the second step portion is higher than the first, and the drain region is positioned in the first step portion and the source region in the second step portion, increasing the distance between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the drain region and source region are positioned close together to reduce device dimensions, then device miniaturization is achieved, but punch-through occurs when high voltage is applied
Solution Approach 1:
The patent introduces a vertical dimension by forming the drain region and source region at different heights on the substrate surface. The drain region is positioned at a first height while the source region is positioned at a second height, creating a height difference that increases the effective distance between them. This dimensional change allows the regions to be vertically separated while maintaining horizontal compactness, thereby preventing punch-through while achieving device miniaturization.
Solution Approach 2:
The patent applies local quality by creating a non-uniform substrate surface with varying heights at different locations. The substrate surface includes a first region at a first height and a second region at a second height, allowing the drain and source regions to be positioned at different vertical levels. This localized height variation enables selective vertical separation of the drain and source regions while maintaining other areas of the device at standard dimensions.
2Reliability
If the drain region and source region are separated vertically to prevent punch-through, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent employs preliminary action by forming a thickness-adjusted insulating film before forming the active regions. This insulating film is deposited with varying thickness in different regions of the substrate, creating a pre-prepared height difference between the first and second regions. Subsequent processing steps then form the drain and source regions at these pre-established different heights, simplifying the overall fabrication process by preparing the vertical structure in advance rather than requiring complex post-processing to create the height difference.
Data Source
AI summary
A semiconductor device includes a substrate, a gate structure, a drain region and a source region. The substrate includes a first step structure. The first step structure includes a first step portion, a connecting portion and a second step portion arranged sequentially along a direction, and the second step portion is higher than the first step portion. The gate structure is disposed on the connecting portion. The drain region is disposed in the first step portion. The source region is disposed in the second step portion.