Oxide Semiconductor Transistor with Buffer Layer for Leakage Control
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Solution Overview
Problem
Current semiconductor devices face challenges in achieving high-speed response and low power consumption due to limitations in on-state characteristics and leakage current suppression, particularly in transistors with oxide semiconductor films.
Innovation Solution
The semiconductor device incorporates a transistor with a channel formation region using an oxide semiconductor containing conductive metal oxides like titanium oxide, indium, and zinc, along with buffer layers to improve field-effect mobility and reduce leakage current, featuring a crystalline oxide semiconductor layer and dopant regions for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an oxide semiconductor film is used as a channel formation region to improve field-effect mobility, then on-state characteristics improve, but leakage current increases due to parasitic channel formation
Solution Approach 1:
The channel formation region is divided into multiple semiconductor layers with different properties: a first semiconductor layer in contact with the gate insulating film providing high field-effect mobility, and a second semiconductor layer providing low off-state current. This segmentation allows each layer to optimize for its specific function, resolving the contradiction between high on-state characteristics and low leakage current.
Solution Approach 2:
Different regions of the channel formation region are assigned different material compositions and properties. The first semiconductor layer uses an oxide semiconductor with specific characteristics for high mobility near the gate interface, while the second semiconductor layer uses a different composition to suppress parasitic channel formation and reduce leakage current in other regions.
2Speed
If the oxide semiconductor layer is made thinner to reduce parasitic capacitance, then high-speed operation is achieved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
Instead of using a single thin oxide semiconductor layer that is difficult to control, the channel is segmented into multiple layers with different thicknesses. The first semiconductor layer can be made thinner for high-speed operation, while the second semiconductor layer provides a thicker, more easily manufactured region that suppresses leakage and compensates for manufacturing variations.
Data Source
AI summary
A semiconductor device including an oxide semiconductor can have stable electric characteristics and high reliability. A transistor in which an oxide semiconductor layer containing indium, titanium, and zinc is used as a channel formation region and a semiconductor device including the transistor are provided. As a buffer layer in contact with the oxide semiconductor layer, a metal oxide layer containing an oxide of one or more elements selected from titanium, aluminum, gallium, zirconium, hafnium, and a rare earth element can be used.