MISFET Gate Insulator Thickness Gradient for Reliability and Speed
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In MISFETs using high dielectric constant gate insulating films, the side end portions of the films come into direct contact with sidewalls, leading to a reduction in dielectric constant and insulation properties, deteriorating device characteristics and reliability.
Innovation Solution
A MISFET structure where the high dielectric constant gate insulating film is kept under sidewalls with a smaller thickness than under the gate electrode, maintaining continuity and reducing capacitance between gate and drain regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the high dielectric constant gate insulating film is kept under sidewalls to prevent direct contact, then device characteristics and reliability are improved, but capacitance between gate and drain regions increases reducing circuit speed
Solution Approach 1:
The patent applies local quality by creating a thickness gradient in the high dielectric constant gate insulating film. The film is thinnest at the gate electrode end, thicker at the drain end, and thickest under the sidewalls. This localized variation in thickness allows the film to provide different functions in different regions: maintaining reliability under sidewalls while minimizing capacitance impact on circuit speed in the active channel region.
2Manufacturing precision
If extension implantation is performed through high dielectric constant film, then desired device characteristics can be obtained, but implantation acceleration energy must be increased causing expansion of implanted impurity in depth direction
Solution Approach 1:
The patent uses local quality by creating a thinner region of the high dielectric constant gate insulating film at the gate electrode end. This localized thinning allows extension implantation to be performed with lower acceleration energy through this specific region, preventing excessive deepening of the extension junction while still maintaining the overall protective function of the thicker film in other regions.
3Ease of manufacture
If side end portions of high dielectric constant gate insulating film are in direct contact with sidewalls, then manufacturing is simplified, but dielectric constant and insulation property are reduced deteriorating device characteristics
Solution Approach 1:
The patent applies local quality by creating a thicker region of the high dielectric constant gate insulating film specifically under the sidewalls. This localized thickening ensures that the film maintains its high dielectric constant and insulation properties where it contacts the sidewalls, preventing degradation of device characteristics while still allowing the sidewall formation process to proceed efficiently.
Data Source
AI summary
A semiconductor device includes: a high dielectric constant gate insulating film formed on an active region in a substrate; a gate electrode formed on the high dielectric constant gate insulating film; and an insulating sidewall formed on each side surface of the gate electrode. The high dielectric constant gate insulating film is continuously formed so as to extend from under the gate electrode to under the insulating sidewall. At least part of the high dielectric constant gate insulating film located under the insulating sidewall has a smaller thickness than a thickness of part of the high dielectric constant gate insulating film located under the gate electrode.