Oxide Semiconductor Nonvolatile Memory for Leakage Reduction
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Solution Overview
Problem
Nonvolatile memory elements using silicon-based semiconductor materials face challenges in achieving stable reading operations due to increased leakage current as the number of memory cells connected to one bit line increases, limiting the size expansion of memory cell arrays and reducing the proportion of area occupied by the peripheral circuit.
Innovation Solution
A nonvolatile memory element utilizing an oxide semiconductor as the material for the channel formation region, with a charge accumulation layer insulated by a second insulating film, and a control gate separated by a first insulating film, allowing for reduced leakage current and stable operation, particularly suitable for large-capacity memory devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of memory cells connected to one bit line is increased to expand memory capacity, then the memory cell array size can be enlarged, but the leakage current of non-selected memory cells increases and reading operation stability deteriorates
Solution Approach 1:
The patent changes the material parameter of the channel formation region from conventional silicon-based semiconductor to oxide semiconductor. This material parameter change fundamentally alters the electrical characteristics, enabling extremely low off-current (less than 1×10^-21 A) which allows stable reading operations even when many memory cells are connected to a single bit line, thus resolving the contradiction between memory capacity expansion and reading stability
2Quantity of substance
If the number of memory cells per bit line is increased, then memory capacity is improved, but the proportion of area occupied by peripheral circuit is reduced
Solution Approach 1:
By changing the semiconductor material parameter to oxide semiconductor with extremely low off-current characteristics, the patent enables higher integration density where more memory cells can be connected per bit line. This reduces the need for peripheral circuits such as sense amplifiers and control logic, thereby decreasing the peripheral circuit area proportion while increasing memory capacity
Data Source
AI summary
A device including a novel nonvolatile memory element is provided. A device including a nonvolatile memory element in which an oxide semiconductor is used as a semiconductor material for a channel formation region. The nonvolatile memory element includes a control gate, a charge accumulation layer which overlaps with the control gate with a first insulating film provided therebetween, and an oxide semiconductor layer formed using an oxide semiconductor material, which overlaps with the charge accumulation layer with a second insulating film provided therebetween.