Vertical Body-Contact FET Structure for Floating-Body Suppression
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Solution Overview
Problem
Current vertical FETs face challenges with the floating-body effect causing threshold voltage shifts and increased off-current, and the implementation of a body contact to suppress this effect often degrades device performance by increasing channel thickness and compromising short channel control, with difficulties in fabricating high-quality body contacts.
Innovation Solution
A vertical semiconductor device with a body contact is designed, featuring a gate stack overlapping the channel region laterally and a body contact layer on the opposite side to apply a body bias, with carefully controlled spacing and doping to manage the floating-body effect without degrading performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a body contact is added to suppress the floating-body effect, then the threshold voltage stability is improved, but the channel thickness increases and device performance degrades
Solution Approach 1:
The patent transitions from a planar body contact to a vertical body contact structure that extends along the channel length. This dimensional change allows the body contact to suppress the floating-body effect through vertical doping while maintaining a thin horizontal channel thickness, thereby improving threshold voltage stability without degrading device performance
Solution Approach 2:
The patent applies localized doping through the vertical body contact at specific regions along the channel, creating non-uniform doping distribution. This local quality enhancement suppresses the floating-body effect where needed while preserving the thin channel structure and short channel control in other regions
2Reliability
If a body contact is added to suppress the floating-body effect, then the off current is reduced, but the fabrication complexity increases
Solution Approach 1:
The patent merges the body contact formation with the existing vertical device fabrication process by integrating the vertical doping step into the sequence of forming the active region and gate stack. This consolidation reduces fabrication complexity while achieving off-current reduction through effective floating-body effect suppression
3Reliability
If the channel thickness is increased to accommodate a body contact, then the floating-body effect is suppressed, but the short channel control is degraded
Solution Approach 1:
The patent resolves this contradiction by changing the body contact geometry from horizontal to vertical, extending along the channel length rather than increasing channel thickness. This dimensional transformation enables floating-body effect suppression while maintaining thin channel thickness and excellent short channel control
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
The solution effectively suppresses the floating-body effect while maintaining device performance by applying a body bias through a strategically positioned body contact, allowing for precise control of the channel region and reducing off-current.
Implementation Method 1
a body contact layer disposed on a second side of the active region opposite to the first side in the lateral direction, so as to overlap with the middle portion of the active region to apply a body bias to the active region
Implementation Method 2
a gate stack disposed on a first side of the active region in a lateral direction with respect to the substrate, so as to at least overlap with the middle portion of the active region
Implementation Method 3
respectively driving a dopant in the first source/drain defining layer, a dopant in the body contact defining layer and a dopant in the second source/drain defining layer into corresponding portions of the active layer
Data Source
AI summary
Disclosed are a vertical semiconductor device with a body contact, a manufacturing method, and an electronic apparatus. The semiconductor device includes: an active region vertically disposed on a substrate, including lower and upper source/drain regions, and a middle portion between lower and upper source/drain regions for defining a channel region; a gate stack on a first side of the active region in a lateral direction to at least overlap with the middle portion; and a body contact layer on a second side of the active region opposite to the first side in the lateral direction to overlap with the middle portion to apply a body bias to the active region. In a vertical direction, distances between a part of the middle portion overlapping with the body contact layer and the lower source/drain region and between the part and the upper source/drain region are first and second spacing distances, respectively.