Oxide Semiconductor Memory Cell for Low Leakage Multilevel Storage
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Solution Overview
Problem
Conventional semiconductor memory devices using silicon substrates face challenges in storing multilevel data due to high leakage and large circuit area, which affects retention characteristics and efficiency.
Innovation Solution
A semiconductor memory device utilizing a memory cell with an oxide semiconductor substrate, including a select transistor and a capacitance element, that stores charge corresponding to coupling weights, enabling multilevel data storage with improved retention and reduced leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon substrate is used in a conventional semiconductor memory device, then the device can store data, but it suffers from high leakage and large circuit area which deteriorates retention characteristics
Solution Approach 1:
The patent changes the material parameter of the substrate from silicon to oxide semiconductor, which fundamentally alters the electrical characteristics. This material substitution reduces leakage current by several orders of magnitude while maintaining the memory function, directly resolving the contradiction between reliability and energy loss.
Solution Approach 2:
The patent employs a composite structure combining oxide semiconductor substrate with metal electrodes (such as tungsten or copper) and insulation films. This composite approach leverages the low-leakage property of oxide semiconductors while using metals for high-conductivity connections, optimizing both retention characteristics and circuit performance.
2Productivity
If a silicon substrate is used in a conventional semiconductor memory device, then the device can store data, but it requires large circuit area which reduces efficiency
Solution Approach 1:
By changing the substrate material to oxide semiconductor, the patent achieves higher charge retention capability per unit area. This allows for more efficient use of circuit area, as each memory cell can maintain its state longer without requiring larger storage capacitors or refresh circuits, thereby improving storage efficiency.
3Quantity of substance
If multilevel data storage is implemented using conventional silicon-based memory, then data capacity increases, but leakage and circuit area increase which degrades performance
Solution Approach 1:
The oxide semiconductor substrate enables multilevel data storage by providing distinct, stable charge states that can represent multiple data levels. The material's inherent low-leakage property ensures that each charge level is maintained reliably over time, allowing high data capacity without sacrificing retention characteristics.
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 memory device effectively stores multilevel data with high retention characteristics and reduced leakage, suppressing the increase in circuit area, thus providing a high-quality memory solution.
Implementation Method 1
a capacitance element configured to store a charge
Implementation Method 2
a transistor formed of an oxide semiconductor
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes a memory cell including a transistor formed of an oxide semiconductor, an insulation film, and a control electrode, and a capacitance element configured to store a charge, the memory cell being configured to store a coupling weight of a neuron model by a charge amount accumulated in the capacitance element; and a control circuit configured to output a signal as a sum of a product between input data of the memory cell and the coupling weight.