Oxide Semiconductor Memory Cell for Long Data Retention
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Solution Overview
Problem
Conventional semiconductor memory devices face challenges in maintaining data retention over long periods without power, requiring frequent refresh operations and high voltage for writing, and suffer from limited write cycles due to transistor leakage and gate insulating layer deterioration.
Innovation Solution
A semiconductor device utilizing an oxide semiconductor material with significantly reduced off-state current, featuring a p-channel type writing transistor and a semiconductor material for the reading transistor, allowing for long-term data retention without refresh operations and unlimited write cycles, eliminating the need for high voltage and reducing gate insulating layer deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a flash memory uses a floating gate to store data, then data holding period becomes extremely long and refresh operation is not needed, but the gate insulating layer deteriorates due to tunneling current after a predetermined number of writing operations
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 extremely low leakage current without requiring high voltage tunneling, thus achieving both long data holding period and unlimited write cycles by eliminating the gate insulating layer deterioration problem
Solution Approach 2:
The patent creates a hybrid memory structure that copies the advantageous characteristics of both volatile and nonvolatile memory. By using oxide semiconductor transistor with near-zero off-state current, it replicates the data retention capability of nonvolatile memory while maintaining the write speed and cycle life of volatile memory, effectively creating a new category of memory that combines the best features of both
2Ease of manufacture
If a DRAM uses a transistor to store electric charge, then writing operation is simple, but the transistor leakage current causes short data holding period 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 off-state current characteristics. This parameter change enables the transistor to maintain extremely low leakage current without requiring high voltage tunneling, thus achieving both long data holding period and unlimited write cycles by eliminating the gate insulating layer deterioration problem
Solution Approach 2:
The patent creates a hybrid memory structure that copies the advantageous characteristics of both volatile and nonvolatile memory. By using oxide semiconductor transistor with near-zero off-state current, it replicates the data retention capability of nonvolatile memory while maintaining the write speed and cycle life of volatile memory, effectively creating a new category of memory that combines the best features of both
3Reliability
If a flash memory uses high voltage to inject charge into the floating gate, then data can be stored, but the writing speed is slow and complex circuits are required
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 extremely low leakage current without requiring high voltage tunneling, thus achieving both long data holding period and unlimited write cycles by eliminating the gate insulating layer deterioration problem
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 low power consumption, high-speed operation, and unlimited write cycles, while avoiding the limitations of conventional nonvolatile memory devices.
Implementation Method 1
a semiconductor device including a nonvolatile memory cell including a writing transistor which includes an oxide semiconductor, and a reading transistor which includes a semiconductor material different from that of the writing transistor
Data Source
AI summary
A semiconductor device including a nonvolatile memory cell including a writing transistor which includes an oxide semiconductor, a reading transistor which includes a semiconductor material different from that of the writing transistor, and a capacitor is provided. Data is written to the memory cell by turning on the writing transistor and supplying a potential to a node where a source electrode (or a drain electrode) of the writing transistor, one electrode of the capacitor, and a gate electrode of the reading transistor are electrically connected to each other, and then turning off the writing transistor so that a predetermined amount of charge is held at the node. Further, when a p-channel transistor is used as the reading transistor, a reading potential is a positive potential.