Combined-Source MOS Transistor with Comb-Shaped Gate
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Solution Overview
Problem
Conventional MOSFETs face challenges with increasing off-state leakage current and power consumption due to short-channel effects and subthreshold slope limitations as feature sizes shrink, while Schottky Barrier and Tunneling Field Effect Transistors struggle with low on-state current and leakage issues.
Innovation Solution
A combined-source MOS transistor with a comb-shaped gate structure that integrates a Schottky junction and band-to-band tunneling mechanism, enhancing tunneling area and turn-on current while minimizing leakage current through precise control of the comb-shaped gate and Schottky source region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the device size is reduced to nanometer scale, then integration density is improved, but off-state leakage current increases due to short-channel effects
Solution Approach 1:
The gate is segmented into multiple comb fingers that extend into the source region, creating multiple independent tunneling paths. This segmentation increases the effective tunneling area while maintaining compact device footprint, enabling higher integration density without exacerbating leakage through any single path
Solution Approach 2:
The gate structure transitions from a planar 2D configuration to a 3D comb-shaped structure that extends vertically and laterally into the source region. This dimensional change increases the gate-source overlap area and tunneling interface without proportionally increasing the device planar footprint, thus improving integration density while controlling leakage
2Use of energy by stationary object
If the threshold voltage is lowered to reduce power consumption, then power consumption is improved, but subthreshold leakage current increases due to limited subthreshold slope
Solution Approach 1:
The conventional thermal carrier injection mechanism is replaced with quantum mechanical band-to-band tunneling through the heavily doped source region. This substitution enables steeper subthreshold slope characteristics because tunneling current can be more sharply controlled by gate voltage, allowing lower threshold voltage without proportionally increasing subthreshold leakage
Solution Approach 2:
The source region doping concentration is changed to very heavy doping levels, fundamentally altering the energy band structure and enabling efficient band-to-band tunneling. This parameter change creates a tunneling transistor characteristic with improved subthreshold slope that decouples the relationship between threshold voltage and subthreshold leakage current
3Object-generated harmful factors
If a Schottky Barrier MOSFET structure is used to lower source and drain parasitic resistance, then parasitic resistance is improved, but on-state current decreases due to large off-state leakage current and small tunneling area
Solution Approach 1:
The invention merges the Schottky barrier structure with a comb-shaped gate configuration, combining the low parasitic resistance benefit of Schottky contacts with the high on-state current capability of increased tunneling area. The multiple comb fingers create multiple parallel tunneling paths that collectively provide high current drive while the Schottky barrier maintains low series resistance
Solution Approach 2:
The gate structure extends into the third dimension by projecting comb fingers into the source region, increasing the tunneling interface area without proportionally increasing the device planar area. This dimensional change enables high on-state current through increased tunneling area while maintaining compact geometry that preserves low parasitic resistance
4Object-generated harmful factors
If a Tunneling Field Effect Transistor structure is used to achieve low leakage current and low subthreshold slope, then leakage current is improved, but on-state current decreases due to limited source junction tunneling probability and tunneling area
Solution Approach 1:
The gate is divided into multiple comb fingers that create multiple independent tunneling junctions in parallel. This segmentation increases the total effective tunneling area proportionally, thereby increasing on-state current while each individual tunneling junction maintains the low leakage characteristics of TFET operation
Solution Approach 2:
The comb-shaped gate extends into the source region, adding vertical and lateral dimensions to the tunneling interface. This dimensional expansion increases the tunneling area available for carrier injection, directly increasing on-state current while the heavily doped source region maintains efficient band-to-band tunneling with low leakage
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 achieves a higher turn-on current, steeper subthreshold slope, and reduced parasitic resistance, compatible with existing CMOS processes, making it suitable for low power consumption applications.
Implementation Method 1
a turn-on is realized by using a direct tunneling of carriers in the source
Implementation Method 2
The TFET uses the gate to control the band-to-band tunneling of a reversed-biased P-I-N junction so as to realize the turn-on
Data Source
AI summary
The present invention discloses a combined-source MOS transistor with a Schottky Barrier and a comb-shaped gate structure, and a method for manufacturing the same. The combined-source MOS transistor includes: a control gate electrode layer, a gate dielectric layer, a semiconductor substrate, a highly-doped source region and a highly-doped drain region, wherein a Schottky source region is connected to a side of the highly-doped source region which is far from a channel, one end of the control gate extends to the highly-doped source region, the extended gate region is an extension gate in a form of a comb-shaped and the original control gate region is a main gate; an active region covered by the extension gate is also a channel region, and is a substrate material; the highly-doped source region which is formed by highly doping is located on both sides of each comb finger of the extension gate; and a Schottky junction is formed at a location where the Schottky source region and the channel under the extension gate are located. As compared with an existing MOSFET, in the invention, a higher turn-on current, a lower leakage current and a steeper subthreshold slope may be obtained under the same process condition and the same active region size.