MOSFET Trench Gate Well Layer for Recovery Loss Reduction
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Solution Overview
Problem
Conventional semiconductor devices with trench gate structures experience increased recovery loss due to electric field concentration at the bottom of trenches, leading to hole generation by dynamic avalanche, which is not sufficiently reduced by existing solutions.
Innovation Solution
A semiconductor device with a MOSFET structure that includes a trench gate structure where the portion of the trench protruding into the drift layer is entirely covered with a well layer of the second conductivity type, connected to the channel layer, which suppresses electric field concentration and hole generation during recovery operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a trench gate structure is used, then device performance is improved, but electric field concentration occurs at the bottom of trenches causing increased recovery loss
Solution Approach 1:
The patent applies local quality by forming a well layer with different conductivity type (second conductivity type) than the drift layer (first conductivity type) specifically at the bottom of the trench. This creates a localized region with different electrical properties that suppresses electric field concentration and hole generation, thereby reducing recovery loss while maintaining the overall trench gate structure performance.
2Reliability
If the trench protrudes into the drift layer, then channel control is improved, but electric field concentration and hole generation increase
Solution Approach 1:
The well layer is formed locally at the bottom of the trench where it protrudes into the drift layer, creating a targeted modification that maintains channel control benefits while suppressing harmful electric field concentration and hole generation in the specific region where these problems occur.
Solution Approach 2:
The patent converts the potentially harmful protruding trench structure into a beneficial configuration by filling it with a well layer of opposite conductivity type. This transforms the source of electric field concentration into a region that actively suppresses such concentration, turning the structural feature that caused problems into a solution.
Data Source
AI summary
A semiconductor device includes a MOSFET including a drift layer, a channel layer, a trench gate structure, a source layer, a drain layer, a source electrode, and a drain electrode. The trench gate structure includes a trench penetrating the channel layer and protruding into the drift layer, a gate insulating film disposed on a wall surface of the trench, and a gate electrode disposed on the gate insulating film. A portion of the trench protruding into the drift layer is entirely covered with a well layer, and the well layer is connected to the channel layer.