Fringeless Transistor Gate Structure for Mixed-Voltage Integration
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Solution Overview
Problem
Providing field effect transistors that operate at different operating voltages at a high device density is a challenge in semiconductor devices.
Innovation Solution
A semiconductor structure comprising multiple field effect transistors with specific gate electrode and trench isolation structures, along with dielectric material layers, is developed to achieve high device density and efficient operation at various voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple field effect transistors with different operating voltages are integrated to increase device density, then device density is improved, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The gate electrode is segmented into multiple portions (first gate electrode portion, second gate electrode portion, third gate electrode portion) with different materials and thicknesses. Each portion is selectively positioned over specific trench isolation structures to create transistors with different operating voltages from a single continuous gate layer structure, thereby increasing device density while managing manufacturing complexity through a unified formation process
Solution Approach 2:
Different regions of the gate electrode structure are assigned different local properties: the first gate electrode portion has greater thickness over first trench isolation structures, the second gate electrode portion has intermediate thickness over second trench isolation structures, and the third gate electrode portion has minimal or no thickness over third trench isolation structures. This local variation in gate thickness creates different threshold voltages for adjacent transistors, enabling high-density integration of mixed-voltage devices
2Adaptability or versatility
If gate electrode thickness is varied to create different operating voltages, then operating voltage diversity is improved, but manufacturing precision requirements increase
Solution Approach 1:
Trench isolation structures are formed first with predetermined heights and positions before depositing the gate electrode material. The gate electrode portions are then deposited to specific thicknesses that correspond to the underlying trench isolation structure heights, ensuring that the final gate thickness variation is precisely controlled by the pre-formed trench structures rather than requiring direct thickness control during gate deposition
Solution Approach 2:
The trench isolation structures serve as intermediary elements that mediate between the single continuous gate electrode deposition process and the final multi-voltage transistor configuration. By controlling the trench isolation structure heights, the patent indirectly controls the effective gate thickness and thus the operating voltage, simplifying the manufacturing precision requirements compared to direct gate thickness control
Data Source
AI summary
A lateral extent of a gate electrode of a field effect transistor along a gate electrode direction that is perpendicular to a channel direction can be the same as a width of an underlying active region. A gate electrode of an additional field effect transistor may extend over a trench isolation structure that laterally surrounds the additional field effect transistor. Different types of electrodes may be formed by patterning a lower gate material layer and by patterning an upper gate material layer with different patterns such that patterned portions of the lower gate material layer are confined within areas of active regions, while patterned portions of the upper gate material layer extends outside of the areas of the active regions.