NMOS Transistor Gate Isolation for Continuous Diffusion Layers
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Solution Overview
Problem
The miniaturization of semiconductor elements leads to significant STI structure stress, affecting the driving capability of transistors, particularly in PMOS and NMOS transistors, where the diffusion layer length influences ON current, and elongating this length for NMOS transistors complicates element isolation and handling.
Innovation Solution
The semiconductor device employs a gate structure that extends orthogonally over N-type diffusion layers to isolate NMOS transistors, allowing for longer diffusion layer lengths without using STI structures, thereby improving ON current characteristics and enabling efficient element isolation and handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If STI structures are used to isolate NMOS transistors, then element isolation is achieved, but diffusion layer length is limited and ON current characteristics deteriorate
Solution Approach 1:
The invention extracts the isolation function from STI structures and assigns it to gate structures instead. By removing the constraint of using STI structures for NMOS isolation, the diffusion layer can extend continuously without interruption, achieving both isolation and long diffusion layer length for improved ON current characteristics.
Solution Approach 2:
The gate structure is given a dual function: it serves both as the gate electrode for the NMOS transistor and as the isolation structure between adjacent NMOS transistors. This multi-functionality eliminates the need for separate STI structures and enables continuous diffusion layer formation.
2Reliability
If diffusion layer length is elongated for NMOS transistors, then ON current characteristics improve, but element isolation and handling become complicated
Solution Approach 1:
The invention segments the isolation function from the diffusion layer continuity. By using gate structures positioned between NMOS transistors as isolation elements, the diffusion layer can maintain continuous long-length formation while isolation is achieved through the segmented gate structure placement, simplifying handling compared to continuous STI isolation.
3Reliability
If STI structures are used for element isolation, then transistor separation is achieved, but chip area efficiency decreases and design flexibility is reduced
Solution Approach 1:
The invention merges the gate structure with the isolation structure function. By combining these two elements into one, the chip area is optimized as the gate structure serves dual purposes, eliminating the need for additional STI structures and improving design flexibility for transistor placement and circuit configuration.
Data Source
AI summary
A semiconductor device includes a plurality of PMOS transistors formed on a semiconductor substrate; and a plurality of NMOS transistors formed on the semiconductor substrate. The plurality of PMOS transistors are electrically isolated from each other by a device isolation structure formed in the semiconductor substrate. The plurality of NMOS transistors are continuously formed in a first direction such that a sequence of N-type diffusion layers of the plurality of NMOS transistors extends in the first direction. One of the plurality of PMOS transistors and one of the plurality of NMOS transistors share a gate electrode.