Semiconductor Source/Drain Structure with Segmented Insulating Layers
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Solution Overview
Problem
In CMOS semiconductor devices, dopants in the source/drain regions diffuse into the substrate, causing capacitance loss, short channel effects, and leakage, which are not effectively addressed by existing technologies.
Innovation Solution
A semiconductor device structure is formed with a gate stack, channel region, and source/drain regions, where a second semiconductor layer is sandwiched between the channel region and the source/drain sidewall, and an insulating layer is placed between the source/drain bottom and the substrate, preventing dopant diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SOI technology with buried oxide layer is used to prevent dopant diffusion, then dopant diffusion is effectively prevented, but device structure and manufacturing process become complex
Solution Approach 1:
The patent divides the isolation structure into multiple segments: a first insulating layer at the bottom, a second insulating layer in the middle, and a third insulating layer at the top. This segmented approach provides effective dopant diffusion prevention while avoiding the need for complex SOI buried oxide structures, thus resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent applies different insulating materials at different locations within the source/drain region. The first insulating layer uses a material with higher etch selectivity than the second semiconductor layer, while the second insulating layer uses a material with higher etch selectivity than the third insulating layer. This local differentiation of material properties enables precise control of dopant diffusion at critical interfaces without requiring complex overall structure.
2Ease of manufacture
If source/drain regions are formed directly in substrate, then manufacturing process is simple, but dopants diffuse into substrate causing capacitance loss and short channel effects
Solution Approach 1:
The patent forms the first insulating layer at the bottom of the source/drain region before introducing dopants. This preliminary isolation structure prevents dopants from diffusing into the substrate during subsequent processing steps, thereby maintaining device performance while keeping the manufacturing process relatively simple and avoiding the need for complex SOI wafer preparation.
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 structure maintains carrier transfer paths while preventing dopant diffusion into the substrate, thereby alleviating capacitance loss and short channel effects.
Implementation Method 1
an insulating layer being sandwiched between the semiconductor substrate and the other portions of the bottom and/or the other portions of the sidewall
Implementation Method 2
a second semiconductor layer being sandwiched between the channel region and a portion of the sidewall distant from the bottom
Data Source
AI summary
The present invention provides a semiconductor device, which is formed on a semiconductor substrate, comprising a gate stack, a channel region, and source/drain regions, wherein the gate stack is on the channel region, the channel region is in the semiconductor substrate, the source/drain regions are embedded in the semiconductor substrate, and each of the source/drain regions comprises a sidewall and a bottom, a second semiconductor layer being sandwiched between the channel region and a portion of the sidewall distant from the bottom, a first semiconductor layer being sandwiched between the semiconductor substrate and at least a portion of the bottom distant from the sidewall, and an insulating layer being sandwiched between the semiconductor substrate and the other portions of the bottom and/or the other portions of the sidewall. The present invention also provides a method for forming the semiconductor device. The present invention helps preventing the dopants in the source/drain regions from diffusing into the substrate.