Oxide Semiconductor Transistor Driving Method for Low Leakage Memory
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Solution Overview
Problem
Conventional semiconductor devices face limitations in data retention time and power consumption due to high off-state current and the need for frequent refresh operations in volatile memory, while non-volatile flash memories suffer from limited write cycles and high voltage requirements.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor with a low off-state current, featuring a writing transistor and a reading transistor of a different material, allowing data to be stored and retrieved without the need for frequent refresh and with reduced power consumption, eliminating the limitations of write cycles and high voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a volatile storage device (DRAM) is used to store data, then the writing operation is simple and fast, but the data holding period is short and refresh operations are required frequently
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 gate voltage without refresh operations while keeping the writing operation simple and fast, thus resolving the contradiction between writing speed and data holding period.
2Duration of action of moving object
If a non-volatile storage device (flash memory) is used to store data, then the data holding time is extremely long and refresh operations are not needed, but the gate insulating layer deteriorates by tunneling current after a predetermined number of writing operations
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor, which dramatically reduces off-state current to 10^-21 to 10^-24 A. This parameter change eliminates the need for high-voltage tunneling current used in flash memory, allowing indefinite rewriting without gate insulating layer deterioration, thus resolving the contradiction between data holding time and reliability.
Solution Approach 2:
The patent replaces the expensive and limited-life flash memory structure with a simpler transistor-capacitor structure using oxide semiconductor. The oxide semiconductor transistor acts as a low-leakage switch that can be rewritten indefinitely without the tunneling current damage that limits flash memory lifetime, making the storage cell more durable for frequent rewriting.
3Duration of action of moving object
If a floating gate structure is used in flash memory, then data can be stored non-volatily, but high voltage is necessary to inject or remove electric charge and a circuit therefor is required
Solution Approach 1:
The patent extracts and eliminates the floating gate structure from the memory cell, replacing it with a simple transistor-capacitor structure. The oxide semiconductor transistor's extremely low off-state current naturally holds the charge on the capacitor without requiring a floating gate or high-voltage injection circuits, thus reducing device complexity while maintaining non-volatile storage capability.
4Use of energy by moving object
If a volatile storage device is used, then power consumption can be reduced by not supplying power, but stored data is lost when power is not supplied
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor with extremely low off-state current (10^-21 to 10^-24 A). This parameter change enables the device to hold data without power supply for extended periods (10 years or more) while consuming minimal standby power, thus resolving the contradiction between power consumption and data retention by achieving non-volatile characteristics in a low-power structure.
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 minimal power consumption, high-speed data operations, and extended device lifespan without the need for high voltage or complex peripheral circuits.
Implementation Method 1
an oxide semiconductor material, which is a wide-gap semiconductor, is used. When a semiconductor material which allows a sufficient reduction in off-state current of a transistor is used
Data Source
AI summary
A semiconductor device with a novel structure and a driving method thereof are provided. A semiconductor device includes a non-volatile memory cell including a writing transistor including an oxide semiconductor, a reading p-channel transistor including a semiconductor material different from that of the writing transistor, and a capacitor. Data is written to the memory cell by turning on the writing transistor so that a potential is supplied to a node where a source electrode of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected, and then turning off the writing transistor so that a predetermined amount of electric charge is held in the node. In a holding period, the memory cell is brought into a selected state and a source electrode and a drain electrode of the reading transistor are set to the same potential, whereby the electric charge stored in the node is held.