T-Shaped Gate Electrode for Field-Effect Transistors
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Solution Overview
Problem
There is a need for improved device structures and methods for forming field-effect transistors, particularly in CMOS technology, to enhance performance and reduce electrical losses, especially when using silicon-on-insulator substrates.
Innovation Solution
A method involving the formation of a gate electrode with a narrow section over a first dielectric layer and a wide section over a second dielectric layer, where the second layer is laterally recessed relative to the first layer, creating a T-shaped gate electrode structure that improves electrical isolation and operational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional gate electrode structure is used in SOI-based FETs, then the device structure is simpler, but the electrical isolation and operational speed are insufficient
Solution Approach 1:
The gate electrode is divided into two distinct sections: a first gate electrode section and a second gate electrode section, with the second section having a larger width than the first. This segmentation allows each section to serve different functional purposes, improving electrical isolation and operational speed while managing structural complexity through purposeful division.
Solution Approach 2:
The invention introduces a width dimension variation in the gate electrode structure, where the second gate electrode section extends wider than the first section. This dimensional change enhances the effective gate control area and improves electrical isolation without significantly increasing overall device footprint, thereby improving speed while controlling complexity.
2Reliability
If the second dielectric layer is laterally recessed to create a T-shaped gate, then electrical isolation and speed improve, but manufacturing complexity increases
Solution Approach 1:
The dielectric layer is segmented into a first dielectric layer and a second dielectric layer, with the second layer being laterally recessed relative to the first. This segmentation creates the T-shaped gate electrode structure that improves electrical isolation. The process uses standard semiconductor fabrication techniques to manage manufacturing complexity.
Solution Approach 2:
The lateral recessing of the second dielectric layer creates a localized structural variation that enhances electrical isolation specifically at the gate region. This local quality change improves reliability without requiring global structural modifications, thereby controlling the increase in manufacturing complexity.
3Loss of energy
If a T-shaped gate electrode is formed with lateral recessing, then electrical losses are reduced, but the number of fabrication steps increases
Solution Approach 1:
The invention changes the geometric parameters of the gate electrode structure by laterally recessing the second dielectric layer to create a T-shape configuration. This parameter change reduces electrical losses by improving field control and reducing parasitic effects. The process integrates these parameter changes into existing fabrication workflows to minimize impact on productivity.
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 approach enables field-effect transistors to operate at higher speeds with reduced electrical losses and improved electrical isolation, enhancing their performance and efficiency.
Implementation Method 1
the second dielectric layer is laterally recessed relative to the first dielectric layer inside the opening with a selective etching process so as to widen a portion of the opening extending vertically through the second dielectric layer
Data Source
AI summary
Device structures for a field-effect transistor and methods for forming a device structure for a field-effect transistor. A first dielectric layer is formed, and a second dielectric layer are formed on the first dielectric layer. An opening is formed that extends vertically through the first and second dielectric layers. After the first opening is formed, the second dielectric layer is laterally recessed relative to the first dielectric layer with a selective etching process, which widens a portion of the opening extending vertically through the second dielectric layer relative to a portion of the opening extending vertically through the first dielectric layer. After the second dielectric layer is laterally recessed, a gate electrode is formed that includes a narrow section in the portion of the opening extending vertically through the first dielectric layer and a wide section in the portion of the opening extending vertically through the second dielectric layer.