Semiconductor Device Channel Extension Region
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Solution Overview
Problem
Conventional high-voltage semiconductor devices require complex structures and high fabrication processes due to the combination of LDMOS and EDMOS transistors, making them difficult to implement and costly to produce, with limited flexibility in using either transistor type for desired operating characteristics.
Innovation Solution
A semiconductor device with a channel extension region that allows the LDMOS transistor to be used as an analog device by varying its channel length, and an impurity region that decreases the effective channel length of the EDMOS transistor to match that of the LDMOS, enabling both transistors to be used as switching devices while maintaining breakdown voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LDMOS transistor uses double diffusion method to form short channel region, then switching device performance is improved, but channel length cannot be varied limiting analog device usage
Solution Approach 1:
The channel region is segmented into two distinct parts: a first channel region formed by double diffusion method with short channel length for switching operation, and a second channel region formed by epitaxial growth with adjustable channel length for analog operation. This segmentation allows each region to be optimized independently for its specific function, resolving the contradiction between switching performance and analog adaptability.
2Adaptability or versatility
If EDMOS transistor is used as analog device with variable channel length, then analog device functionality is achieved, but structure complexity and fabrication difficulty increase
Solution Approach 1:
The LDMOS transistor is designed with dual functionality by incorporating both a first channel region for switching operation and a second channel region for analog operation. The gate electrode can control current flow through either region depending on the applied voltage, allowing a single device structure to perform both switching and analog functions, thereby eliminating the need for separate EDMOS transistor structures.
3Productivity
If EDMOS transistor channel length is decreased to match LDMOS, then both transistors can be used as switching devices, but breakdown voltage characteristics deteriorate
Solution Approach 1:
The patent applies different quality characteristics to different regions of the transistor. The first channel region has short channel length optimized for switching performance, while the second channel region has longer channel length optimized for breakdown voltage characteristics. By locally optimizing each region's properties rather than uniformly designing the entire channel, both switching capability and breakdown voltage reliability are maintained.
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
Simplifies the structure of high-voltage semiconductor devices, reduces production costs and time, and improves current characteristics by providing regions with different threshold voltage levels, allowing for increased on-current and decreased off-current.
Implementation Method 1
The channel region C1 of the LDMOS transistor is formed by selecting impurities having different diffusion characteristic and applying a double diffusion method
Implementation Method 2
an impurity region that decreases the effective channel length of the EDMOS transistor to match that of the LDMOS
Data Source
AI summary
A semiconductor device includes a second conductive-type well configured over a substrate, a first conductive-type body region configured over the second conductive-type well, a gate electrode which overlaps a portion of the first conductive-type body region, and a first conductive-type channel extension region formed over the substrate and which overlaps a portion of the gate electrode.