Trench-Gate Semiconductor Device With Localized Insulating Film Thickness
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Solution Overview
Problem
Existing semiconductor devices with trench-gate structures face challenges in maintaining reliable transistor performance due to excessive etching of materials outside the gate trench, increased channel resistance, and electric field concentration, which affects yield and reliability.
Innovation Solution
A semiconductor device with a trench-gate structure featuring a gate insulating film that is thicker on the surface than on the side surfaces, and an overhang portion at the upper edge to disperse electric fields, ensuring the gate electrode overlaps the source layer and preventing insulation breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the gate insulating film is made uniformly thick on all inner surfaces of the gate trench, then the manufacturing process is simpler, but electric field concentration occurs at the upper and lower corner portions of the trench reducing withstand voltage
Solution Approach 1:
The gate insulating film is designed with different thicknesses at different locations: a first thickness on the side surface and a second thickness (greater than the first) at the upper and lower corner portions. This local variation in thickness distributes the electric field more evenly, preventing concentration at corners while maintaining manufacturing feasibility through controlled deposition processes
2Manufacturing precision
If excessive etching is performed outside the gate trench to remove material, then the trench-gate structure is better defined, but the gate electrode may not reliably overlap with the source layer affecting transistor operation
Solution Approach 1:
The gate insulating film is formed with extended thickness at the upper corner portion before the gate electrode is deposited. This preliminary thickening creates a buffer zone that ensures the gate electrode will reliably overlap with the source layer even if subsequent etching processes remove some material, thereby maintaining transistor operation performance
3Reliability
If the gate insulating film is made thicker at the upper edge to disperse electric fields, then the withstand voltage improves, but the amount of carriers induced near the side surface of the gate trench in the channel layer decreases increasing channel resistance
Solution Approach 1:
The gate insulating film thickness is locally optimized: thicker at the upper and lower corner portions to disperse electric fields and improve withstand voltage, while maintaining an appropriate first thickness on the side surface to preserve carrier induction in the channel layer. This selective thickness variation balances electrical breakdown protection with transistor conduction performance
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 enhances transistor performance, improves yield, reduces channel resistance, and maintains reliability by dispersing electric fields, thereby improving the ON-state voltage and preventing insulation breakdown.
Implementation Method 1
a gate insulating film formed conformal to an inner surface of the gate trench and the surface of the semiconductor layer, and a gate electrode embedded inside the gate trench interposed by the gate insulating film
Data Source
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AI summary
This semiconductor device includes: a semiconductor layer having a structure in which a drain layer of a first conductivity type, a channel layer of a second conductivity type, and a source layer of a first conductivity type are layered in the stated order, the source layer being exposed on the outer surface of the semiconductor layer; a gate trench that passes through the source layer and through the channel layer from the outer surface of the semiconductor layer, the deepest section of the gate trench reaching the drain layer; a gate insulating film formed on the inside surface of the gate trench, the gate insulating film being formed correspondingly with respect to the outer surface of the semiconductor layer; and a gate electrode embedded inside the gate trench interposed by the gate insulating layer. A portion of the gate insulating film that abuts the outer surface of the semiconductor layer is thicker than a portion that abuts the channel layer at a side surface of the gate trench.