Gain Cell Memory Layout With Shared Dummy Transistor
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Solution Overview
Problem
Static random access memory (SRAM) requires a large area overhead due to its layout design rule differences from logic circuits and the need for a dummy region, limiting the storage capacity of memory devices.
Innovation Solution
A logic-compatible memory device with improved area efficiency is achieved by using a gain cell memory design that shares a dummy transistor between neighboring memory cells, reducing footprint area and enhancing data retention through increased equivalent capacitance of storage capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SRAM is used for memory devices, then operation speed is improved, but area overhead increases
Solution Approach 1:
The patent merges the dummy transistor with the storage transistor by connecting the source/drain terminal of the storage transistor to the gate terminal of the dummy transistor, forming a storage node. This integration eliminates the need for separate dummy regions while maintaining data retention functionality, thereby reducing area overhead while preserving SRAM's high-speed operation characteristics
Solution Approach 2:
The dummy transistor serves multiple functions: it acts as a storage element through its gate capacitor, provides data retention through the storage node, and enables logic circuit compatibility. This multi-functionality reduces the overall area requirement compared to traditional SRAM designs that require separate dummy regions
2Ease of manufacture
If dummy region is added to separate SRAM from logic circuits, then layout compatibility is improved, but storage capacity increases
Solution Approach 1:
The invention combines the dummy transistor structure with the storage transistor structure, eliminating the need for separate dummy regions. The storage node formed by connecting the storage transistor's source/drain terminal to the dummy transistor's gate terminal serves both as a storage element and as a separator between logic circuits, thereby maintaining layout compatibility while increasing storage capacity
Solution Approach 2:
The dummy transistor is nested within the memory cell structure itself, with its gate terminal forming the storage node. This nested configuration allows the dummy transistor to be integrated within the memory cell footprint rather than requiring additional external dummy regions, thus increasing storage capacity while maintaining layout compatibility
Data Source
AI summary
A memory device is provided. The memory device includes: a write transistor, with a gate terminal connected to a write word line, and having a first source/drain terminal connected to a bit line; a storage transistor, with a gate terminal coupled to a second source/drain terminal of the write transistor to form a storage node, and having a first source/drain terminal connected to a source line; and a read transistor, with a gate terminal coupled to a read word line, and having a first source/drain terminal connected to the bit line. The read transistor and the storage transistor share a second source/drain terminal.