Oxide Semiconductor Memory Device for Non-Volatile Data Retention
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Solution Overview
Problem
Current semiconductor memory devices face challenges such as high power consumption, limited data retention, and degradation of memory elements due to off-state current and tunneling current, especially in volatile and non-volatile memory types like DRAM and flash memory.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor with a potential change circuit that reduces off-state current, allowing for long-term data retention without the need for frequent refresh operations and eliminating the limitations on the number of writing cycles, by using a structure with transistors and capacitors connected in a specific configuration to manage charge holding and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If a volatile memory device (DRAM) is used to store data, then the device can be manufactured with lower cost and simpler structure, but power consumption increases due to frequent refresh operations and data is lost when power is stopped
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor, which fundamentally alters the off-state current characteristics. This parameter change enables the transistor to maintain an off state with extremely low leakage current, eliminating the need for frequent refresh operations and enabling non-volatile data storage without requiring complex additional circuits
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor material with conventional semiconductor materials in a single memory device. The oxide semiconductor transistor serves as the storage element while maintaining compatibility with standard memory cell architectures, achieving both volatile and non-volatile memory characteristics in one device
2Reliability
If high voltage is applied to hold charge in floating gate, then data can be stored non-volatily, but writing and erasing speed decreases and additional circuits are required
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor, which enables non-volatile data storage through extremely low off-state current rather than through high voltage charge injection. This eliminates the need for high voltage operation and associated charge injection/removal processes, thereby achieving non-volatile storage with conventional low voltage operation and high speed
Solution Approach 2:
The patent extracts and eliminates the floating gate structure and high voltage charge injection mechanism from the memory device. By using oxide semiconductor transistor characteristics alone, the device achieves non-volatile storage without the complex high voltage charge trapping and removal mechanisms required by flash memory
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 solution enables low power consumption, extended data retention, and high-speed operation without the need for high voltage, thereby improving the reliability and integration density of semiconductor memory devices.
Implementation Method 1
an oxide semiconductor material, which is a wide gap semiconductor, is used
Implementation Method 2
When a semiconductor material which allows a sufficient reduction in off-state current of a transistor is used, the semiconductor device can hold data for a long period
Implementation Method 3
a potential change circuit which is configured to selectively control the potential of the source lines in order to decrease power consumption
Data Source
Figure 1A-1~1B
Figure 2
Figure 3
AI summary
An object is to provide a semiconductor device with a novel structure in which stored data can be held even when power is not supplied, and the number of times of writing is not limited. The semiconductor device is formed using a wide gap semiconductor and includes a potential change circuit which selectively applies a potential either equal to or different from a potential of a bit line to a source line. Thus, power consumption of the semiconductor device can be sufficiently reduced.