Trench Gate Oxide Layout for High-Voltage LDMOS Density
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Solution Overview
Problem
Conventional LDMOS transistor devices face challenges in improving electrical performance, reliability, and density of high voltage semiconductor units, particularly in reducing the area occupied and enhancing breakdown voltage.
Innovation Solution
A semiconductor device with a gate structure that includes gate oxide layers of different thicknesses, where a portion of the gate electrode is disposed in a trench within the semiconductor substrate, and the thicker second gate oxide layer is positioned vertically between the gate electrode and the substrate, reducing the device's area and improving electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDMOS transistor device uses a lateral-diffused drift region with low doping concentration and large area to achieve high breakdown voltage, then the electrical performance and reliability are improved, but the area occupied by the device increases and device density decreases
Solution Approach 1:
The patent transitions from a conventional planar gate structure to a trench-based three-dimensional gate structure. The gate electrode is positioned within a trench formed in the drift region, allowing the gate to extend vertically into the substrate. This dimensional change enables better electric field control and higher breakdown voltage while maintaining a compact footprint, thus improving device density without sacrificing reliability
Solution Approach 2:
The patent implements different gate oxide layer thicknesses in different regions: a first gate oxide layer with a first thickness and a second gate oxide layer with a second thickness greater than the first. This local quality variation allows optimization of the electric field distribution at the gate edge, reducing field concentration and improving breakdown voltage while maintaining compact device dimensions
2Ease of manufacture
If the gate structure uses uniform gate oxide layer thickness to simplify manufacturing, then the ease of manufacture is improved, but the electrical performance and reliability at the gate edge deteriorate due to high electric field concentration
Solution Approach 1:
The patent implements different gate oxide layer thicknesses in different regions: a first gate oxide layer with a first thickness and a second gate oxide layer with a second thickness greater than the first. This local quality variation allows optimization of the electric field distribution at the gate edge, reducing field concentration and improving breakdown voltage while maintaining compact device dimensions
Solution Approach 2:
The gate oxide layer is segmented into two distinct regions with different thicknesses. The first gate oxide layer is formed in the trench region, and the second gate oxide layer is formed outside the trench. This segmentation allows each region to be optimized for its specific function: the thinner first layer reduces area, while the thicker second layer improves electrical performance at the gate edge
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a trench, and a gate structure. The trench is disposed in the semiconductor substrate. The gate structure is disposed on the semiconductor substrate. The gate structure includes a gate electrode, a first gate oxide layer, and a second gate oxide layer. A first portion of the gate electrode is disposed in the trench, and a second portion of the gate electrode is disposed outside the trench. The first gate oxide layer is disposed between the gate electrode and the semiconductor substrate. At least a portion of the first gate oxide layer is disposed in the trench. The second gate oxide layer is disposed between the second portion of the gate electrode and the semiconductor substrate in a vertical direction. A thickness of the second gate oxide layer is greater than a thickness of the first gate oxide layer.