MOSFET Drift Region Layout for Lower Output Capacitance
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Solution Overview
Problem
Existing semiconductor devices, such as MOSFETs, face challenges in reducing electrostatic capacitance, which affects their switching performance and efficiency in power conversion applications.
Innovation Solution
The semiconductor device incorporates a p−-type drift region and a first conductive part with impurities of mutually-different conductivity types, increasing the work function of the conductive part and reducing electrostatic capacitance by spreading the depletion layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional MOSFET structure is used, then device simplicity is maintained, but electrostatic capacitance cannot be reduced sufficiently
Solution Approach 1:
The device is divided into multiple semiconductor regions with different conductivity types (first conductivity type, second conductivity type, third conductivity type) arranged in alternating layers. This segmentation creates multiple junctions that spread the depletion layer and reduce electrostatic capacitance between electrodes, thereby reducing switching losses while maintaining reasonable structural complexity
Solution Approach 2:
Different semiconductor regions are doped with impurities of different conductivity types at different locations. The first conductive part contains impurities of the second conductivity type while the gate electrode contains impurities of the first conductivity type. This local differentiation of electrical properties creates favorable potential distributions that reduce electrostatic capacitance without requiring complete structural redesign
2Loss of energy
If electrostatic capacitance is reduced by increasing depletion layer, then switching performance improves, but work function requirements become more stringent
Solution Approach 1:
The work function of the first conductive part is increased by introducing impurities of the second conductivity type, which is opposite to the conductivity type of the drift region. This parameter change in impurity concentration and conductivity type directly increases the work function, enabling the depletion layer to spread more effectively and reduce electrostatic capacitance while maintaining reliable electrical characteristics
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 configuration reduces the output capacitance and reverse transfer capacitance, leading to lower switching losses and improved efficiency in semiconductor devices.
Implementation Method 1
increasing the work function of the conductive part and reducing electrostatic capacitance by spreading the depletion layer
Implementation Method 2
reducing electrostatic capacitance by spreading the depletion layer
Data Source
AI summary
According to one embodiment, a semiconductor device includes first and second electrodes, first to third semiconductor regions, a first conductive part, a first gate electrode. The first semiconductor region is located on the first electrode and electrically connected with the first electrode. The second semiconductor region is located on the first semiconductor region. The third semiconductor region is located on a portion of the second semiconductor region. The first conductive part is located in the first semiconductor region with a first insulating part interposed. The first gate electrode is located on the first conductive part with a first inter-layer insulating part interposed. The first gate electrode faces the second semiconductor region via a first gate insulating layer. The second electrode is located on the second and third semiconductor regions and electrically connected with the second and third semiconductor regions, and the first conductive part.