Trench MOSFET Gate Structure With Reduced Gate-Source Capacitance
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Solution Overview
Problem
The trench gate structure in semiconductor devices, such as MOSFETs, experiences reduced switching speed due to enlarged gate-source parasitic capacitance caused by the field plate having the same potential as the source electrode.
Innovation Solution
The semiconductor device incorporates a field plate with a two-layer insulating film structure, which widens the spacing between the control electrode and the field plate, enhancing dielectric strength and reducing parasitic capacitance by using insulating films like silicate glass with boron and phosphorus (BPSG) between the control electrode and the field plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a field plate is provided with the same potential as the source electrode in a trench gate structure, then the device can achieve proper electrical characteristics, but the gate-source parasitic capacitance is enlarged which reduces switching speed
Solution Approach 1:
An insulating film is introduced as an intermediary between the control electrode and the field plate. This insulating film layer physically separates the two conductive elements while maintaining their respective electrical functions, thereby reducing the parasitic capacitance formed between them without compromising the field plate's ability to maintain source potential
Solution Approach 2:
The dielectric properties of the insulating film are optimized to achieve the desired balance between reducing parasitic capacitance and maintaining dielectric strength. By selecting materials with appropriate permittivity and breakdown characteristics, the patent reduces the capacitive coupling between electrodes while ensuring reliable electrical isolation
2Speed
If the spacing between the control electrode and the field plate is increased, then parasitic capacitance is reduced, but the device structure becomes more complex and manufacturing难度 increases
Solution Approach 1:
The insulating film is divided into multiple layers with different materials and functions. This segmentation allows each layer to be optimized for specific purposes (e.g., one layer for primary insulation, another for dielectric strength enhancement), achieving effective capacitance reduction while maintaining a manageable structural complexity through systematic layering
3Speed
If a two-layer insulating film structure is used to reduce parasitic capacitance, then switching speed improves, but the manufacturing process becomes more complex
Solution Approach 1:
The insulating film layers are formed sequentially during the fabrication process, with each layer being deposited and processed before the next is added. This preliminary action approach allows for controlled formation of the multi-layer structure using standard semiconductor manufacturing techniques, making the complex structure achievable through systematic process integration
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 improves the dielectric strength and reduces parasitic capacitance, leading to faster switching speeds and enhanced reliability in semiconductor devices.
Implementation Method 1
a two-layer insulating film structure, which widens the spacing between the control electrode and the field plate, enhancing dielectric strength and reducing parasitic capacitance by using insulating films like silicate glass with boron and phosphorus (BPSG)
Data Source
AI summary
A semiconductor device includes a semiconductor part, first to third electrodes, and a control electrode. The first electrode is provided on a back surface of the semiconductor part. The second electrode is provided at a front surface side of the semiconductor part. The third electrode and the control electrode are provided inside a trench of the semiconductor part. The control electrode includes first and second control portions. The semiconductor device further includes first to third insulating films. The first insulating film is between the control electrode and the semiconductor part. The second insulating film covers the first and second control portions. The third insulating film is between the second electrode and the second insulating film. The third insulating film includes a portion extending between the first and second control portions. The third electrode is between the first electrode and the extension portion of the third insulating film.