Trench Oxide Semiconductor Transistor Curved Corner Design
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Solution Overview
Problem
Miniaturization of semiconductor devices leads to the short-channel effect, which causes degradation in electrical characteristics, particularly in oxide semiconductor transistors, due to difficulty in controlling threshold voltage and increased leakage current.
Innovation Solution
A semiconductor device with an oxide semiconductor film provided along a trench in an insulating layer, where the trench has curved corner portions with specific curvature radii, and the oxide semiconductor film includes crystals with a c-axis perpendicular to the surface, allowing for controlled channel length and reduced short-channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the transistor channel length is reduced to achieve miniaturization, then the device size and power consumption are improved, but the short-channel effect causes degradation in electrical characteristics and threshold voltage control
Solution Approach 1:
The invention introduces a vertical dimension by forming the semiconductor layer within a trench structure extending from the surface into the substrate. This three-dimensional configuration allows the channel length to be defined by the trench depth rather than the lateral distance between source and drain electrodes, enabling miniaturization in the planar direction while maintaining sufficient channel length vertically to suppress short-channel effects
Solution Approach 2:
The invention applies curvature to the corner portions of the trench, specifically forming the semiconductor layer to contact the curved corner regions. This curvature ensures complete coverage of the semiconductor layer over the trench structure, including the corner portions, which prevents defects and ensures uniform electrical characteristics throughout the channel region
2Area of stationary object
If the transistor is miniaturized to increase integration density, then the device area is reduced, but the leakage current increases due to short-channel effects
Solution Approach 1:
By transitioning from a planar channel structure to a vertical trench-based channel structure, the invention achieves area reduction in the lateral direction while maintaining adequate channel length in the vertical direction. This dimensional transition allows miniaturization without the associated increase in leakage current that plagues conventional planar short-channel devices
3Manufacturing precision
If the oxide semiconductor film is formed to contact the trench corner portions, then the channel length control is improved, but the manufacturing precision requirements increase due to the need for specific curvature radii
Solution Approach 1:
The invention specifies a curvature radius parameter for the trench corner portions (20 nm to 60 nm) that optimizes the balance between achieving complete semiconductor layer coverage and maintaining manufacturability. This parameter control enables precise channel length definition while keeping the manufacturing process within reasonable complexity limits
Data Source
AI summary
A semiconductor device having a transistor including an oxide semiconductor film is disclosed. In the semiconductor device, the oxide semiconductor film is provided along a trench formed in an insulating layer. The trench includes a lower end corner portion and an upper end corner portion having a curved shape with a curvature radius of longer than or equal to 20 nm and shorter than or equal to 60 nm, and the oxide semiconductor film is provided in contact with a bottom surface, the lower end corner portion, the upper end corner portion, and an inner wall surface of the trench. The oxide semiconductor film includes a crystal having a c-axis substantially perpendicular to a surface at least over the upper end corner portion.