Semiconductor Gate Electrode Depletion Layer Design
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Solution Overview
Problem
Conventional semiconductor devices with gate electrodes having a depletion layer only on one end suffer from insufficient gate field suppression in the drift layer region and increased parasitic capacitance between the gate electrode and substrate due to the limited extent of the depletion layer.
Innovation Solution
A semiconductor device design featuring a gate electrode composed of two regions: a high-conductivity impurity region and a lower-conductivity depletion layer forming region, where the depletion layer is formed over a significant portion of the gate electrode between the end closer to the drain and the center, allowing for improved electric field relaxation and reduced parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the depletion layer is formed only on the end of the gate electrode, then the electric field between the gate electrode and drain region is reduced, but the gate field suppression in the drift layer region is insufficient and parasitic capacitance increases
Solution Approach 1:
The gate electrode is designed with non-uniform impurity concentration distribution, creating different regions: a first region with high impurity concentration for maintaining electrode functionality, and a second region with low impurity concentration for forming depletion layers. This local quality variation allows the gate electrode to simultaneously achieve adequate gate field suppression and reduced parasitic capacitance.
Solution Approach 2:
The gate electrode is segmented into multiple functional regions along its length. The first region (closer to source) maintains high conductivity for proper gate control, while the second region (closer to drain) forms depletion layers to reduce parasitic capacitance and improve withstand voltage. This segmentation resolves the contradiction by assigning different properties to different segments.
2Device complexity
If the depletion layer is formed only on the end of the gate electrode, then the structure is simple, but the gate field suppression in the drift layer region is insufficient
Solution Approach 1:
The gate electrode employs local quality variation with a gradient impurity concentration profile. The first region has high impurity concentration for strong gate control, while the second region has low impurity concentration for extended depletion layer formation. This resolves the contradiction by achieving better gate field suppression through localized property changes rather than uniform structure.
Solution Approach 2:
The impurity concentration parameter is changed along the length of the gate electrode, creating a gradient from high concentration in the first region to low concentration in the second region. This parameter variation enables the depletion layer to extend further into the drift layer region, improving gate field suppression without requiring a completely different structure.
3Ease of manufacture
If the depletion layer is formed only on the end of the gate electrode, then the manufacturing process is simple, but the parasitic capacitance between gate electrode and substrate is increased
Solution Approach 1:
The non-uniform impurity concentration distribution in the gate electrode is established during the preliminary manufacturing stages (such as ion implantation or in-situ doping during polysilicon deposition). This preliminary action creates the conditions for extended depletion layer formation, which subsequently reduces parasitic capacitance without requiring additional complex manufacturing steps.
Solution Approach 2:
The manufacturing process incorporates local quality variation by doping different regions of the gate electrode with different impurity concentrations. The first region receives high impurity concentration doping while the second region receives low impurity concentration doping, enabling selective depletion layer formation that reduces parasitic capacitance through standard manufacturing techniques.
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 enhances the relaxation of gate fields in the gate insulating film and drift layer, improves the OFF-state voltage resistance of transistors, and reduces parasitic capacitance between the gate electrode and substrate by extending the depletion layer across a larger area of the gate electrode.
Implementation Method 1
the gate electrode consists of two regions including a first conductivity type second impurity region opposed to the first impurity region and a third impurity region having a lower first conductivity type impurity concentration than the second impurity region or made of an intrinsic semiconductor
Data Source
AI summary
A semiconductor device includes a gate electrode formed through a gate insulating film provided on a first impurity region and a drift layer, and this gate electrode consists of two regions including a first conductivity type second impurity region opposed to the first impurity region and a third impurity region capable of forming a depletion layer.