Trench Gate Insulator Stepped Profile for Nitride Semiconductor
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Solution Overview
Problem
Current semiconductor devices using nitride semiconductors face challenges in achieving optimal normally-off operation with high breakdown voltage and low on-resistance due to issues with surface potential and electric field concentration, particularly at the interface between the gate electrode and the drain electrode.
Innovation Solution
A semiconductor device design featuring a gate electrode placed in a trench with a gate insulating film having a stepped structure, where the insulating film retreats from the end portion of the trench on the drain side, creating a two-stage thickness profile, which disperses electric field concentration and reduces channel resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a gate recess is made on the back side relative to the hetero junction to achieve normally-off operation, then the breakdown voltage is improved, but the on-resistance increases
Solution Approach 1:
The patent applies local quality by creating a stepped structure of the gate insulating film with different thicknesses in different regions. The first region has a thinner insulating film while the second region has a thicker insulating film, allowing localized optimization of electrical characteristics to simultaneously achieve low on-resistance and high breakdown voltage
Solution Approach 2:
The patent introduces a dimensional change by creating a stepped (two-stage) thickness profile of the gate insulating film rather than using a uniform thickness. This dimensional variation in the insulating film thickness allows for simultaneous optimization of conflicting electrical parameters
2Reliability
If the gate insulating film thickness is increased to reduce leakage current, then the breakdown voltage is improved, but the channel control capability deteriorates
Solution Approach 1:
The patent applies local quality by creating a stepped structure of the gate insulating film with different thicknesses in different regions. The first region has a thinner insulating film while the second region has a thicker insulating film, allowing localized optimization of electrical characteristics to simultaneously achieve low on-resistance and high breakdown voltage
Solution Approach 2:
The gate insulating film is segmented into two distinct regions with different thicknesses. This segmentation allows the first region to provide good channel control while the second region provides leakage current suppression, resolving the contradiction between control capability and reliability
3Productivity
If the device size is reduced for high integration, then the productivity is improved, but the electric field concentration increases
Solution Approach 1:
The patent applies local quality by creating a stepped structure of the gate insulating film with different thicknesses in different regions. The first region has a thinner insulating film while the second region has a thicker insulating film, allowing localized optimization of electrical characteristics to simultaneously achieve low on-resistance and high breakdown voltage
Data Source
AI summary
A semiconductor device includes a first nitride semiconductor layer formed over a substrate, a second nitride semiconductor layer formed over the first nitride semiconductor layer and having a band gap wider than a band gap of the first nitride semiconductor layer, a trench penetrating through the second nitride semiconductor layer and reaching an inside of the first nitride semiconductor layer, a gate electrode placed in the trench over a gate insulating film, and a first electrode and a second electrode formed over the second nitride semiconductor layer on both sides of the gate electrode, respectively.