Fringeless Transistor Circuits for Multi-Voltage Memory Density
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Solution Overview
Problem
Developing field effect transistors that operate at different operating voltages while maintaining high device density is a challenge in semiconductor technology, particularly for memory device applications.
Innovation Solution
A semiconductor structure comprising a field effect transistor with a trench isolation structure, a gate dielectric, a gate electrode, and a conductive gate cap structure, where the gate electrode does not extend beyond the active region, allowing for efficient voltage operation and high density integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If field effect transistors are designed to operate at different operating voltages, then voltage versatility is improved, but device density deteriorates
Solution Approach 1:
The gate electrode is segmented into two distinct portions: a first portion that contacts the active region and a second portion that extends beyond it. This segmentation allows different voltage levels to be applied to different segments, enabling the transistor to operate at multiple voltage levels while maintaining high device density through compact layout.
Solution Approach 2:
The gate electrode extends in a direction perpendicular to the channel length direction, utilizing the width dimension to provide additional functional capability. This dimensional extension allows the gate to control voltage at multiple levels without increasing the channel length, thereby maintaining high device density while achieving voltage versatility.
2Ease of operation
If gate electrode extends beyond active region, then voltage control capability is improved, but manufacturing precision deteriorates
Solution Approach 1:
The gate electrode is formed to extend beyond the active region boundaries during the fabrication process, before final patterning and alignment steps. This preliminary extension ensures that sufficient gate material is available for subsequent processing steps, and the final precise alignment is achieved through controlled patterning that defines the exact boundaries of the gate electrode portions.
Solution Approach 2:
The gate electrode serves as an intermediary structure that bridges the active region and the surrounding isolation structures. By extending beyond the active region, it provides a transition zone that facilitates voltage control while the trench isolation structure acts as a mediator to define precise boundaries and maintain manufacturing precision through its laterally extending portions.
Data Source
AI summary
A field effect transistor includes a gate dielectric and a gate electrode overlying an active region and contacting a sidewall of a trench isolation structure. The transistor may be a fringeless transistor in which the gate electrode does not overlie a portion of the trench isolation region. A planar dielectric spacer plate and a conductive gate cap structure may overlie the gate electrode. The conductive gate cap structure may have a z-shaped vertical cross-sectional profile to contact the gate electrode and to provide a segment overlying the planar dielectric spacer plate. Alternatively or additionally, a conductive gate connection structure may be provided to provide electrical connection between two electrodes of adjacent field effect transistors.