Oxide Semiconductor Transistor Nonvolatile SRAM
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Solution Overview
Problem
Current semiconductor devices lack a nonvolatile memory solution with low off-state current, leading to issues with data retention and power consumption, particularly in applications where power is intermittently available.
Innovation Solution
A semiconductor device with a nonvolatile memory configuration utilizing transistors with a channel formation region made from an oxide semiconductor layer, which has a small off-state current, preventing electric charge leakage and allowing data retention even when power is off, by using a specific circuit configuration and manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transistor is used in SRAM configuration, then the device operates as volatile memory with higher off-state current, but power consumption increases and data retention fails when power is off
Solution Approach 1:
The patent changes the material parameter of the transistor channel 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 off-state current (less than 10^-21 A/μm) while preserving transistor functionality, thereby achieving nonvolatile memory operation with improved data retention and reduced power consumption
2Loss of energy
If oxide semiconductor transistor is used, then off-state current is reduced to achieve nonvolatile memory, but manufacturing complexity increases
Solution Approach 1:
The patent segments the semiconductor device into distinct functional regions: an oxide semiconductor layer region for the transistor channel and a silicon semiconductor region for other circuit components. This segmentation allows each region to be optimized independently - the oxide semiconductor region for low off-state current and the silicon region for conventional high-speed operation - while simplifying the overall manufacturing process by allowing separate processing steps for each material type
Solution Approach 2:
The patent employs a composite semiconductor structure combining oxide semiconductor and silicon semiconductor materials in the same device. The oxide semiconductor layer forms the transistor channel while silicon regions provide support functions. This composite approach leverages the complementary strengths of both materials - the ultra-low off-state current of oxide semiconductor and the mature fabrication processes of silicon - thereby reducing overall manufacturing complexity compared to using oxide semiconductor throughout the entire device
Data Source
AI summary
A nonvolatile memory is provided. A semiconductor device (a nonvolatile memory) has a circuit configuration similar to that of a general SRAM. By providing a transistor whose off-state current is small between a stored data holding portion and a power supply line of the SRAM, leakage of electric charge from the stored data holding portion is prevented. As the transistor whose off-state current is small provided for preventing leakage of electric charge from the stored data holding portion, a transistor including an oxide semiconductor film is preferably used. Such a configuration can also be applied to a shift register, whereby a shift register with low power consumption can be obtained.