Oxide Semiconductor Memory Cell for Data Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor memory devices face challenges in maintaining data retention over long periods without power, experiencing high power consumption due to leakage currents, and suffering from limited write cycles and high voltage requirements, which restrict their application in frequent data rewriting scenarios.
Innovation Solution
A semiconductor device utilizing a widegap semiconductor material, such as oxide semiconductors, with a novel structure comprising writing, reading, and selecting transistors, which reduces off-state current, eliminating the need for refresh operations and high voltage writing, allowing for unlimited write cycles and efficient data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a DRAM structure is used to store data in capacitors, then writing operation is simple, but data holding period becomes short due to leakage current and refresh operation is necessary
Solution Approach 1:
The invention changes the material parameter of the transistor from conventional semiconductor to oxide semiconductor, which fundamentally alters the off-state current characteristics. This material parameter change enables the transistor to maintain extremely low leakage current while allowing simple capacitor-based data storage, achieving both easy writing and long data retention without refresh operations
2Duration of action of stationary object
If a flash memory structure with floating gate is used, then data holding period becomes extremely long, but gate insulating layer deteriorates due to tunneling current after predetermined number of writing operations
Solution Approach 1:
The invention changes the transistor material from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics and eliminates tunneling current effects. This material parameter change allows the gate insulating layer to maintain its integrity over unlimited write cycles while preserving long data holding capabilities
Solution Approach 2:
The invention converts the typically harmful tunneling current that causes gate insulating layer deterioration into a beneficial low off-state current characteristic through the use of oxide semiconductor materials. The same physical mechanism that would normally degrade the device is transformed into a feature that enables unlimited write cycles
3Reliability
If high voltage is applied to inject charge into floating gate for writing operations, then data can be stored, but writing speed becomes slow and additional circuits are required
Solution Approach 1:
The invention changes the material parameter from conventional semiconductor to oxide semiconductor, which fundamentally alters the charge storage mechanism. Instead of requiring high voltage for charge injection into a floating gate, the oxide semiconductor transistor maintains data through its intrinsic low off-state current, enabling high-speed writing operations at normal voltages
4Duration of action of stationary object
If SRAM flip-flop circuit is used to hold data, then refresh operation is not needed, but cost per storage capacity becomes high
Solution Approach 1:
The invention changes the transistor material to oxide semiconductor, which enables simple capacitor-based storage to achieve data retention characteristics previously only attainable with complex flip-flop circuits. This material parameter change allows a one-transistor plus capacitor structure to provide both simplicity and long data holding capability
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 operation, and extended write cycle life, overcoming limitations of conventional memory devices by leveraging the low off-state current of oxide semiconductors.
Implementation Method 1
a semiconductor device which includes a write word line, a read word line, a bit line, a source line, a signal line, a memory cell array having a plurality of memory cells, a first driver circuit having a delay circuit electrically connected to the signal line, and a second driver circuit. One of the memory cells includes a first transistor which includes a first gate electrode, a first source electrode, a first drain electrode, and a first channel formation region, a second transistor which includes a second gate electrode, a second source electrode, a second drain electrode, and a second channel formation region, and a third transistor which includes a third gate electrode, a third source electrode, a third drain electrode, and a third channel formation region. The first channel formation region includes a semiconductor material different from that of the second channel formation region.
Data Source
AI summary
An object is to provide a semiconductor device having a novel structure, which can hold stored data even when not powered and which has an unlimited number of write cycles. A semiconductor device includes a memory cell including a widegap semiconductor, for example, an oxide semiconductor. The memory cell includes a writing transistor, a reading transistor, and a selecting transistor. Using a widegap semiconductor, a semiconductor device capable of sufficiently reducing the off-state current of a transistor included in a memory cell and holding data for a long time can be provided.