Oxide Semiconductor Transistor Data Retention
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Solution Overview
Problem
Conventional semiconductor storage devices face limitations in data retention time, require frequent refresh operations due to high off-state current, and have issues with durability and speed in writing and erasing operations, especially in flash memory where the gate insulating layer deteriorates with tunneling current.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor material with low off-state current, which reduces power consumption and eliminates the need for refresh operations, and incorporates a capacitor with increased capacitance per unit area, allowing for long-term data retention without high voltage requirements and without deteriorating the gate insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a conventional transistor is used in a DRAM, then the device can store data using a capacitor, but leakage current flows between source and drain when the transistor is off, causing short data holding period and requiring frequent refresh operations
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor, which has fundamentally different electrical characteristics including extremely low off-state current, thereby extending data holding period and reducing refresh operations
Solution Approach 2:
The patent uses a composite structure combining oxide semiconductor material with conventional semiconductor materials in the transistor channel, leveraging the unique properties of oxide semiconductor to achieve ultra-low leakage current while maintaining compatibility with existing manufacturing processes
2Duration of action of moving object
If flash memory is used for non-volatile storage, then data holding time becomes extremely long and refresh operation is not needed, but the gate insulating layer deteriorates by tunneling current during writing operations, limiting the number of writing operations
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor, which operates at lower voltages and does not require high-voltage tunneling current for writing, thereby eliminating the deterioration problem of the gate insulating layer while maintaining non-volatile data storage capability
Solution Approach 2:
The patent replaces the high-voltage tunneling mechanism of flash memory with a low-voltage field-effect mechanism using oxide semiconductor transistors, achieving similar non-volatile storage functionality without the harmful high-voltage effects
3Duration of action of moving object
If flash memory uses high voltage for holding or removing electric charge, then data can be stored non-volatently, but it takes relatively long time to hold or remove charge, making high-speed writing and erasing difficult
Solution Approach 1:
The patent changes the operating voltage parameter from high voltage (flash memory) to low voltage (oxide semiconductor transistor), enabling faster charge/discharge cycles while maintaining non-volatile data retention through the ultra-low off-state current characteristic
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
The semiconductor device achieves long-term data retention with reduced power consumption, high-speed operation, and increased reliability by using oxide semiconductors, eliminating the need for frequent refresh and minimizing wear on the gate insulating layer.
Implementation Method 1
an oxide semiconductor material, which is a wide-gap semiconductor, is used
Implementation Method 2
an oxide semiconductor material has high permittivity; thus, the use of the oxide semiconductor material for a dielectric of a capacitor enables an increase in capacitance per unit area
Data Source
AI summary
An object is to provide a novel semiconductor device which can store data even when power is not supplied in a data storing time and which does not have a limitation on the number of writing operations. The semiconductor device includes a transistor and a capacitor. The transistor includes a first oxide semiconductor layer, a source electrode and a drain electrode which are in contact with the first oxide semiconductor layer, a gate electrode overlapping with the first oxide semiconductor layer, and a gate insulating layer between the first oxide semiconductor layer and the gate electrode. The capacitor includes the source electrode or the drain electrode, a second oxide semiconductor layer in contact with the source electrode or the drain electrode, and a capacitor electrode in contact with the second oxide semiconductor layer.