Nitride Semiconductor Gate Electrode Placement for Drive Loss Reduction
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Solution Overview
Problem
Semiconductor devices formed from nitride semiconductors require high gate drive voltage, leading to increased drive loss due to the need to exceed multiple threshold voltages for on-state operation.
Innovation Solution
A semiconductor device configuration with a selectively positioned gate electrode on the upper surface of the electron supply layer, avoiding the side surface, reduces the gate drive voltage by utilizing a nitride semiconductor structure with a recessed opening and electron transit layer to minimize on-resistance and drive loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional nitride semiconductor transistor structure is used, then the device achieves low on-resistance and high breakdown voltage, but it requires high gate drive voltage which increases drive loss
Solution Approach 1:
The patent applies local quality by creating a selective gate electrode configuration where the gate electrode is positioned only on the upper surface of the electron supply layer in the recessed region, while intentionally leaving the side surface without gate electrode coverage. This localized differentiation allows the channel formation to occur primarily through the upper surface electron supply, reducing the gate drive voltage requirement while maintaining effective channel control for on-off operation.
2Ease of operation
If the gate electrode is formed on both the upper surface and side surface of the electron supply layer, then better channel control is achieved, but the gate drive voltage increases due to multiple threshold voltages
Solution Approach 1:
The patent extracts the gate electrode from the side surface region, removing it from positions where it would create additional threshold voltage requirements. By taking out the gate electrode coverage from the side surface of the electron supply layer and retaining it only on the upper surface, the invention reduces the number of threshold voltages that must be exceeded for device activation, thereby reducing drive loss while preserving essential on-off control functionality.
Data Source
AI summary
A semiconductor device includes: a substrate; a first nitride semiconductor layer disposed on the substrate; a second nitride semiconductor layer disposed on the first nitride semiconductor layer; a first opening penetrating the second nitride semiconductor layer; an electron transit layer and an electron supply layer which are formed along an upper surface of the second nitride semiconductor layer and a recessed surface of the first opening; a gate electrode disposed above the electron supply layer; a second opening penetrating the electron supply layer and the electron transit layer; a source electrode disposed to cover the second opening and electrically connected to the second nitride semiconductor layer; and a drain electrode disposed on a back surface of the substrate. The electron supply layer has a side surface formed along a side surface of the first opening. The gate electrode is not disposed on the side surface of the electron supply layer.