Surrounded Channel Oxide Transistor for Stable Drain Current
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Solution Overview
Problem
Current semiconductor devices using oxide semiconductors face challenges in achieving constant drain current in the saturation region, high on-state current, and stable electric characteristics, particularly in transistors with oxide semiconductor channels.
Innovation Solution
A transistor structure is developed with specific layer configurations, including a first and third oxide semiconductor layer, a second oxide semiconductor layer positioned between them, and a gate electrode overlapping the second oxide semiconductor layer, where the second oxide semiconductor layer has a thickness between 2 nm and 8 nm, and the channel length is greater than 10 nm and less than 1 μm, optimized for high-frequency operation and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional oxide semiconductor transistor structure is used, then the device complexity is low, but the drain current cannot be kept constant in the saturation region
Solution Approach 1:
The oxide semiconductor layer is divided into multiple stacked layers (first oxide semiconductor layer, second oxide semiconductor layer, and third oxide semiconductor layer) with different thicknesses and compositions. This segmentation allows each layer to fulfill specific functions: the first and third layers provide structural support and electrical contact, while the thin second layer (2-8 nm) serves as the active channel that ensures constant drain current in saturation region
Solution Approach 2:
Different regions of the oxide semiconductor structure have different local properties. The second oxide semiconductor layer has a specific thickness range (2-8 nm) and is positioned between the first and third layers, creating localized variations in electrical characteristics. This local quality differentiation enables the thin second layer to provide the desired saturation characteristics while the thicker first and third layers provide structural stability
Data Source
AI summary
A semiconductor device having stable electric characteristics is provided. The transistor includes first to third oxide semiconductor layers, a gate electrode, and a gate insulating layer. The second oxide semiconductor layer has a portion positioned between the first and third oxide semiconductor layers. The gate insulating layer has a region in contact with a top surface of the third oxide semiconductor layer. The gate electrode overlaps with a top surface of the portion with the gate insulating layer positioned therebetween. The gate electrode faces a side surface of the portion in a channel width direction with the gate insulating layer positioned therebetween. The second oxide semiconductor layer includes a region having a thickness greater than or equal to 2 nm and less than 8 nm. The length in the channel width direction of the second oxide semiconductor layer is less than 60 nm.