3D Gate Electrode Overlap for Uniform Channel Length in GAA Transistors
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Solution Overview
Problem
Current semiconductor devices face challenges in achieving uniform electrical characteristics due to deviations in channel length and strain variations caused by source/drain regions, which affect device performance.
Innovation Solution
A semiconductor device design featuring a gate electrode with an overlapped portion that has a side surface inclined toward the substrate, reducing channel length deviations and strain variations by ensuring uniform performance across channel layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional gate electrode structure is used, then the device structure is simple, but channel length deviations and strain variations occur affecting electrical characteristics
Solution Approach 1:
The gate electrode is divided into multiple segments: a main body portion and an overlapped portion that extends over the source/drain structure. This segmentation allows different regions of the gate electrode to serve different functions - the main body provides standard gate control while the overlapped portion compensates for channel length variations and manages strain distribution, thereby improving channel length uniformity without requiring complete structural redesign
Solution Approach 2:
The gate electrode structure transitions from a two-dimensional planar configuration to a three-dimensional structure by adding the overlapped portion that extends in the vertical dimension over the source/drain structure. This dimensional change enables the gate to interact with multiple channel layers at different heights, improving electrical characteristic uniformity across the three-dimensional channel structure
2Manufacturing precision
If the gate electrode overlaps the source/drain structure, then channel length deviations are reduced, but the device structure becomes more complex
Solution Approach 1:
The overlapped portion of the gate electrode is specifically positioned only in regions where channel length deviation occurs, rather than uniformly across the entire device. This localized configuration addresses the specific problem area - where the channel interface with the source/drain structure creates length variations - without adding unnecessary complexity to regions where the standard gate structure already provides adequate control
3Reliability
If source/drain structures are added to improve device performance, then electrical characteristics improve, but strain variations and channel length deviations increase
Solution Approach 1:
The overlapped portion of the gate electrode is designed in advance to counteract the harmful effects that source/drain structures inevitably introduce. By extending the gate over the source/drain structure, the design preemptively compensates for channel length deviations and strain variations before they degrade device performance, allowing the source/drain structures to provide their beneficial electrical characteristics without suffering from their own induced variations
Data Source
AI summary
A semiconductor device includes a substrate including an active region in a first direction, a plurality of channel layers on the active region and disposed in a direction perpendicular to an upper surface of the substrate, a gate electrode respectively surrounding the plurality of channel layers, and a source/drain structure respectively disposed on both sides of the gate electrode in the first direction and connected to each of the plurality of channel layers. The gate electrode extends in a second direction crossing the first direction. The gate electrode includes an overlapped portion in a region of the gate electrode on an uppermost channel layer of the plurality of channel layers. The overlapped portion of the gate electrode overlaps the source/drain structure in the first direction and has a side surface inclined toward the upper surface of the substrate.