Semiconductor Floating Region Inverted U-Shaped Gate Insulator
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Solution Overview
Problem
Conventional semiconductor devices with trench gate structures face challenges in maintaining low ON-resistance while positioning the floating region near the body region, as this can lead to increased ON-resistance due to depletion layer connections.
Innovation Solution
The semiconductor device incorporates a floating region within an inverted U-shaped section of the gate insulator, positioned near the body region, which inhibits the connection between depletion layers and maintains the floating region's size to prevent total depletion, thereby reducing ON-resistance and enhancing withstand voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the floating region is arranged in the vicinity of the body region, then the electric field applied to the gate insulator is relaxed, but the depletion layers from the body region and floating region may connect, causing increased ON-resistance
Solution Approach 1:
An inverted U-shaped section of gate insulator is introduced as an intermediary barrier between the body region and floating region. This structural intermediary physically separates the depletion layers while still allowing the floating region to relax the electric field on the gate insulator, thus preventing depletion layer connection and maintaining low ON-resistance.
Solution Approach 2:
The gate insulator is segmented into a conventional portion and an inverted U-shaped section. The inverted U-shaped section specifically targets the region where depletion layers might connect, creating a physical barrier that segments the electric field paths and prevents harmful depletion layer connection while maintaining the beneficial electric field relaxation effect.
2Strength
If the floating region is positioned closer to the body region, then the withstand voltage characteristic is improved, but the risk of depletion layer connection increases
Solution Approach 1:
The inverted U-shaped gate insulator section serves as a mediator that enables the floating region to be positioned closer to the body region for improved withstand voltage characteristics while simultaneously preventing depletion layer connection. The U-shaped structure creates an electric field barrier that maintains reliability even when the floating region is optimally positioned for voltage withstand.
Solution Approach 2:
The gate insulator is given different local qualities: the inverted U-shaped section provides enhanced insulation and depletion layer separation in the critical region near the body region, while other portions of the gate insulator maintain their conventional structure. This localized modification allows optimal floating region positioning without compromising depletion layer separation.
Data Source
AI summary
A semiconductor substrate of a semiconductor device includes a body region of a first conductivity type, a drift region of a second conductivity type coming into contact with a lower surface of the body region, a gate electrode that is provided in a gate trench passing through the body region and extending to the drift region and faces the body region, and a gate insulator that is provided between the gate electrode and a wall surface of the gate trench. An inverted U-shaped section is formed in a lower surface of the gate insulator, and a floating region of the first conductivity type is formed in the inverted U-shaped section. The floating region protrudes under a portion that is located at a lowermost portion in the lower surface of the gate insulator.