Semiconductor Device With Stacked Gate Electrodes
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Solution Overview
Problem
Field effect transistors using nitride semiconductors face challenges in achieving a threshold voltage comparable to those using silicon semiconductors, with existing structures struggling to maintain low on-resistance and high voltage withstand characteristics while allowing normal-off operation.
Innovation Solution
The semiconductor device incorporates a MIS (Metal Insulator Semiconductor) structure with a recessed gate configuration, featuring a second gate electrode section over a first gate electrode section via an insulating film, which increases the apparent gate voltage and reduces gate leakage current, enabling improved threshold voltage control and switching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If a MIS structure with recessed gate is used to increase threshold voltage, then threshold voltage increases up to three times, but device complexity increases due to additional gate electrode sections and insulating films
Solution Approach 1:
The gate structure is divided into a first gate electrode section and a second gate electrode section, with the second section arranged on the first section via an insulating film. This segmentation allows independent control of different gate regions, enabling threshold voltage adjustment without requiring complete redesign of the entire gate structure.
Solution Approach 2:
The patent introduces a vertical stacking dimension by arranging the second gate electrode section on top of the first gate electrode section through an insulating film. This three-dimensional gate configuration increases the effective gate control area and enables higher threshold voltage without proportionally increasing planar device footprint.
2Area of moving object
If excessive gate drive voltage is applied to achieve higher threshold voltage, then threshold voltage control improves, but gate leakage current increases significantly
Solution Approach 1:
An insulating film is introduced as an intermediary between the first gate electrode section and the second gate electrode section. This insulating layer acts as a barrier that prevents direct electrical contact, thereby suppressing gate leakage current while still allowing the stacked gate structure to function for threshold voltage control.
Solution Approach 2:
The gate structure is divided into separate sections with the insulating film between them, creating electrically isolated regions. This segmentation prevents excessive voltage application from causing direct leakage paths while maintaining the ability to control threshold voltage through the distributed gate structure.
3Productivity
If a normally-off type GaNFET structure is used to reduce on-resistance, then switching characteristics improve, but the gate-to-source structure cannot provide insulation, leading to current flow under excessive voltage
Solution Approach 1:
The insulating film positioned between the first and second gate electrode sections serves as a protective intermediary that provides electrical insulation. This prevents harmful current flow between gate sections under excessive voltage conditions while preserving the normally-off type structure's low on-resistance and fast switching characteristics.
Solution Approach 2:
The insulating film is built into the gate structure beforehand as a protective measure against potential overvoltage conditions. This pre-established insulation barrier prevents damage or unwanted current flow before excessive voltage can cause problems, enhancing device reliability without affecting normal switching operation.
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 allows for a threshold voltage increase of up to three times the original, reducing switching time and stabilizing overall chip performance, while maintaining low gate leakage current and enabling high-voltage, high-current continuous switching operations.
Implementation Method 1
a second gate electrode section which is arranged on the first gate electrode section via an insulating film
Implementation Method 2
a second gate electrode section which is arranged on the first gate electrode section via an insulating film
Data Source
AI summary
A semiconductor device includes a channel layer formed over a substrate, a barrier layer formed on the channel layer and a gate electrode. A second gate electrode section is formed on the gate electrode via a gate insulating film. It becomes possible to make an apparent threshold voltage applied to the second gate electrode of a MISFET higher than an original threshold voltage applied to the gate electrode for forming a channel under the gate electrode by providing an MIM section configured by the gate electrode, the gate insulating film and the second gate electrode in this way.