Oxide Semiconductor Trench Transistor Suppressing Short-Channel Effect
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Solution Overview
Problem
Miniaturization of transistors leads to a short-channel effect, resulting in degraded electric characteristics, high contact resistance, and reduced on-state current due to the direct contact between oxide semiconductor films and electrode layers, which complicates achieving high-speed operation, low power consumption, and high integration.
Innovation Solution
A semiconductor device design where an oxide semiconductor film is formed in a trench with a crystal structure having the c-axis perpendicular to the surface, and impurity regions with higher concentrations are used as source and drain regions, reducing contact resistance and enhancing ohmic contact, while the channel formation region maintains crystallinity to extend effective channel length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a transistor is miniaturized to achieve high-speed operation and low power consumption, then transistor size is reduced, but short-channel effect occurs resulting in degraded electric characteristics
Solution Approach 1:
The patent transitions from a planar transistor structure to a three-dimensional structure by forming the semiconductor film within a trench that extends in the depth direction. This vertical dimension allows the channel length to be extended along the trench depth, effectively increasing the channel length without increasing the planar footprint, thereby suppressing short-channel effects while maintaining miniaturization.
Solution Approach 2:
The semiconductor film is segmented into distinct regions with different impurity concentrations: a first region with lower impurity concentration forming the channel formation region, and a second region with higher impurity concentration forming the source/drain regions. This segmentation allows optimization of each region's electrical properties independently.
2Device complexity
If source electrode layer and drain electrode layer are directly in contact with oxide semiconductor film, then device structure is simplified, but contact resistance increases and on-state current decreases
Solution Approach 1:
The patent applies local quality by creating a second region with higher impurity concentration specifically at the source and drain areas where contact with electrode layers occurs. This localized doping improvement enhances carrier concentration and conductivity at the contact interfaces, reducing contact resistance without affecting the overall device structure complexity.
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 design effectively suppresses the short-channel effect, reduces resistance, and enables high-speed operation, low power consumption, and high integration by maintaining stable electric characteristics and improving ohmic contact between the oxide semiconductor film and electrode layers.
Implementation Method 1
the oxide semiconductor film includes a crystal having the c-axis, which is substantially perpendicular to a surface of the oxide semiconductor film
Implementation Method 2
the oxide semiconductor film is formed in a trench (groove) provided in an insulating layer
Implementation Method 3
The oxide semiconductor film further includes a region whose impurity concentration is higher than that of the channel formation region is formed in a region in contact with an upper end corner portion of the trench
Data Source
AI summary
It is an object to provide a semiconductor device in which a short-channel effect is suppressed and miniaturization is achieved, and a manufacturing method thereof. A trench is formed in an insulating layer and impurities are added to an oxide semiconductor film in contact with an upper end corner portion of the trench, whereby a source region and a drain region are formed. With the above structure, miniaturization can be achieved. Further, with the trench, a short-channel effect can be suppressed setting the depth of the trench as appropriate even when a distance between a source electrode layer and a drain electrode layer is shortened.