Oxide Semiconductor Memory Cell With Capacitor Data Retention
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Solution Overview
Problem
Conventional volatile memory devices require frequent refresh operations due to leakage current and power loss, while non-volatile memory devices face limitations in write endurance and high voltage requirements, making them unsuitable for frequent data rewriting.
Innovation Solution
A semiconductor device utilizing a highly purified oxide semiconductor transistor with extremely low off-current, integrated with a capacitor, allowing data storage without power supply and unlimited write cycles, eliminating the need for high voltage and refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a volatile memory device (DRAM) is used to store data, then data can be read and written quickly, but leakage current causes charge to flow in or out of the capacitor even when the transistor is not selected, requiring frequent refresh operations and increasing power consumption
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-current (less than 1×10^-21 A), thereby eliminating the need for refresh operations and reducing power consumption while maintaining fast read/write speeds
2Duration of action of stationary object
If a non-volatile memory device (flash memory) is used to store data for long time, then data storing time becomes extremely long and refresh operation is not needed, but the gate insulating layer deteriorates by tunneling current after a predetermined number of writing operations, limiting the number of write cycles
Solution Approach 1:
The patent changes the transistor material to oxide semiconductor with extremely low off-current characteristics, enabling non-volatile data storage without the high-voltage tunneling mechanism of flash memory, thus achieving unlimited write cycles while maintaining long data retention time
Solution Approach 2:
The patent replaces the expensive and limited-life floating gate structure with a simple capacitor structure that can be repeatedly written without degradation, effectively making the memory cell disposable in terms of write endurance limitations
3Duration of action of stationary object
If a non-volatile memory device (flash memory) is used to achieve long-term data storage, then refresh operation is not needed, but high voltage is necessary for holding or removing charge from the floating gate, requiring additional circuits and increasing device complexity
Solution Approach 1:
The patent extracts and removes the high-voltage charge pumping circuit and floating gate structure from the memory device, replacing them with a simple capacitor and oxide semiconductor transistor that operate at standard voltages, thereby significantly reducing device complexity while maintaining non-volatile data storage capability
Solution Approach 2:
The patent replaces the complex floating gate structure requiring high-voltage circuits with a simple capacitor structure that operates at standard voltages, effectively simplifying the device architecture while achieving the same data retention function
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 storage with low power consumption, high-speed operation, and no limitations on write cycles, overcoming the limitations of conventional memory devices.
Implementation Method 1
a first channel formation region electrically connected to the first source electrode and the first drain electrode and using an oxide semiconductor material
Implementation Method 2
a transistor formed using a highly purified oxide semiconductor has extremely small leakage current
Data Source
AI summary
An object of the present invention is to provide a semiconductor device having a novel structure in which in a data storing time, stored data can be stored even when power is not supplied, and there is no limitation on the number of writing. A semiconductor device includes a first transistor including a first source electrode and a first drain electrode; a first channel formation region for which an oxide semiconductor material is used and to which the first source electrode and the first drain electrode are electrically connected; a first gate insulating layer over the first channel formation region; and a first gate electrode over the first gate insulating layer. One of the first source electrode and the first drain electrode of the first transistor and one electrode of a capacitor are electrically connected to each other.