Oxide Semiconductor Transistor with SOI Substrate for Low Leakage Memory
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor memory devices face challenges such as high power consumption, limited data retention time, and wear-out issues due to leakage currents and the need for frequent refresh operations in volatile memories, while non-volatile flash memories suffer from gate insulating layer deterioration and high voltage requirements.
Innovation Solution
A semiconductor device using a highly purified oxide semiconductor and single crystal silicon on insulator (SOI) substrate, which forms fully-depleted transistors with extremely low off-state current, eliminating the need for refresh operations and allowing long-term data retention without voltage limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a volatile memory device (DRAM) is used to hold data in a capacitor, then data can be accessed quickly, but power consumption increases and data retention time decreases due to leakage current requiring frequent refresh operations
Solution Approach 1:
The patent changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics to achieve extremely low off-state current. This parameter change enables the transistor to function as an ultra-low leakage switch, resolving the contradiction between fast access and low power consumption in memory applications
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor layer with conventional semiconductor layers (such as silicon) to create a hybrid transistor device. This composite approach leverages the low leakage特性 of oxide semiconductor while maintaining the high mobility and fast switching characteristics of conventional semiconductor, thus resolving the speed-power consumption tradeoff
2Speed
If a volatile memory device (DRAM or SRAM) is used, then data can be accessed with fast speed, but data is lost when power supply stops requiring additional non-volatile memory
Solution Approach 1:
The patent creates a universal memory device that combines both volatile and non-volatile memory characteristics in a single device structure. The oxide semiconductor transistor enables the same device to function as both fast volatile memory during power supply and retain data without power due to extremely low leakage, eliminating the need for separate volatile and non-volatile memory systems
3Duration of action of stationary object
If a non-volatile memory device (flash memory) is used to hold data for long time, then data retention is improved, but the gate insulating layer deteriorates due to tunneling current limiting the number of writing operations
Solution Approach 1:
The patent changes the transistor material parameter from conventional semiconductor to oxide semiconductor, which has fundamentally different electrical characteristics including extremely low off-state current. This parameter change eliminates the tunneling current issue that causes gate insulating layer deterioration in flash memory, enabling unlimited write operations while maintaining non-volatile data storage capability
4Use of energy by moving object
If a non-volatile memory device (flash memory) is used to eliminate refresh operations, then power consumption is reduced, but high voltage is required for charge injection and removal increasing device complexity
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor, which enables low-voltage operation due to its unique electrical characteristics. The extremely low off-state current and high on-state current density of oxide semiconductor transistors allow for effective data storage and retrieval without requiring high voltage charge injection, thus eliminating the need for complex high voltage generation circuits while maintaining low power consumption
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, high integration, and high-speed operation with no limitations on the number of write cycles, improving reliability and reducing circuit size by eliminating the need for capacitors in the plane direction.
Implementation Method 1
a transistor including a channel formation region formed of an oxide semiconductor
Implementation Method 2
an insulating layer formed over the supporting substrate
Data Source
AI summary
An object of one embodiment of the disclosed invention is to provide a semiconductor device having 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 an insulating layer formed over a supporting substrate and, over the insulating layer, a highly purified oxide semiconductor and single crystal silicon which is used as a silicon on insulator (SOI). A transistor formed using a highly purified oxide semiconductor can hold data for a long time because leakage current thereof is extremely small. Further, by using an SOI substrate and utilizing features of thin single crystal silicon formed over an insulating layer, fully-depleted transistors can be formed; therefore, a semiconductor integrated circuit with high added values such as high integration, high-speed driving, and low power consumption can be obtained.