Semiconductor Active Region Height Variation for Transistor Optimization
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Solution Overview
Problem
CMOS devices face challenges in manufacturing due to differing operating characteristics and parameters between p-type and n-type transistors, such as increased junction leakage in n-type transistors when trying to elevate active areas for improved performance, and the difficulty in optimizing processing parameters for both types.
Innovation Solution
The solution involves selectively recessing or elevating isolation regions proximate to active areas of p-type transistors while maintaining coplanarity with n-type transistors, using methods like etching or selective epitaxial growth to create step heights that enhance p-type transistor performance without degrading n-type transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active areas are elevated to improve transistor performance, then effective gate width increases, but junction leakage increases in n-type transistors
Solution Approach 1:
The patent applies local quality by creating different active area heights for different transistor types. PMOS transistors have elevated active areas to improve their performance, while NMOS transistors maintain coplanar active areas to minimize junction leakage. This selective differentiation allows each transistor type to be optimized for its specific characteristics without compromising the other.
2Reliability
If isolation regions are recessed to create step heights, then effective gate width for p-type transistors increases, but manufacturing complexity increases
Solution Approach 1:
The patent implements preliminary action by forming the isolation region recesses during the isolation region formation process itself, before subsequent transistor fabrication steps. The recesses are created using selective epitaxial growth or etching techniques integrated into the existing process flow, avoiding the need for additional complex processing steps after the main transistor structures are formed.
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
This approach optimizes the performance of both p-type and n-type transistors by increasing the effective gate width for p-type transistors while minimizing junction leakage in n-type transistors, allowing for improved device performance and tunability of isolation region recesses.
Implementation Method 1
using methods like etching or selective epitaxial growth to create step heights
Implementation Method 2
using methods like etching or selective epitaxial growth to create step heights
Data Source
AI summary
Semiconductor devices and methods of manufacture thereof are disclosed. In one embodiment, a semiconductor device includes a first transistor having a first active area, and a second transistor having a second active area. A top surface of the first active area is elevated or recessed with respect to a top surface of the second active area, or a top surface of the first active area is elevated or recessed with respect to a top surface of at least portions of an isolation region proximate the first transistor.