Trench-Gate MISFET Gate Electrode Depth and Sidewall Insulation
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Solution Overview
Problem
The reliability of semiconductor devices with trench-gate MISFETs is compromised due to damage to the gate insulating film during ion implantation and etching processes, leading to reduced withstand voltage and increased leak current.
Innovation Solution
A semiconductor device design featuring a trench-gate field effect transistor with a gate electrode positioned lower than the semiconductor substrate surface and a sidewall insulating film formed over the gate electrode and trench sidewall, which protects the gate insulating film from ion implantation and etching, ensuring increased withstand voltage and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ion implantation and etching processes are used in manufacturing, then productivity is improved, but the gate insulating film is damaged leading to reduced reliability
Solution Approach 1:
A sidewall insulating film is introduced as an intermediary protective layer between the gate insulating film and the harmful ion implantation/etching processes. This sidewall insulating film absorbs the damage from ions and etchants, preventing direct contact with the gate insulating film while allowing the necessary manufacturing processes to proceed.
Solution Approach 2:
The sidewall insulating film is formed in advance before the ion implantation and etching processes. This preliminary protective layer is prepared on the sidewalls of the trench structure, ensuring that the gate insulating film is already protected before the damaging processes occur during manufacturing.
2Length of moving object
If gate insulating film thickness is reduced, then device performance is improved, but withstand voltage decreases and leak current increases
Solution Approach 1:
The insulation protection is segmented into two distinct parts: the gate insulating film that is in direct contact with the gate electrode and the sidewall insulating film that provides external protection. This segmentation allows the gate insulating film to be made thinner for performance while the sidewall insulating film compensates for the reduced voltage withstand capability by providing additional protective insulation on the trench sidewalls.
Data Source
AI summary
A semiconductor device with enhanced reliability in which a gate electrode for a trench-gate field effect transistor is formed through a gate insulating film in a trench made in a semiconductor substrate. The upper surface of the gate electrode is in a lower position than the upper surface of the semiconductor substrate in an area adjacent to the trench. A sidewall insulating film is formed over the gate electrode and over the sidewall of the trench. The gate electrode and the sidewall insulating film are covered by an insulating film as an interlayer insulating film.