Dual-Work-Function Gate Structure for Double Hump Suppression

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Solution Overview

Problem

Integrated circuits with narrow channel widths exhibit a bimodal 'double hump' effect in drain current versus gate voltage curves due to depletion layers at isolation region corners, leading to undesirable performance issues.

Innovation Solution

A gate electrode structure is designed with regions of opposite work functions, extending over isolation and active regions, to mitigate the double hump effect by controlling the channel threshold voltage and sheet resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional gate electrode structure is used, then the manufacturing process is simple, but the transistor exhibits a bimodal double hump effect in drain current versus gate voltage curves due to depletion layers at isolation region corners

Engineering Contradiction:

Improvetransistor performanceVSAvoidgate electrode structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The gate electrode is divided into multiple regions with different work functions: a first region over the active region and second regions over the isolation regions. This segmentation allows independent optimization of each region's electrical characteristics to eliminate the double hump effect while maintaining manufacturing feasibility through sequential processing steps.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the gate electrode are assigned different work functions tailored to their specific locations: the first region has a work function optimized for the active region channel control, while the second regions have work functions optimized for the isolation region depletion layer control. This local quality differentiation resolves the electrical performance issue without requiring complete restructuring of the device.

Inventive Principle:

Principle #3Local quality

2Reliability

If the gate electrode extends over isolation regions, then the depletion layers at corners are controlled, but the sheet resistance and threshold voltage become difficult to optimize

Engineering Contradiction:

Improvethreshold voltage controlVSAvoidwork function optimization

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The work function parameter is varied across different regions of the gate electrode by using different materials or doping levels. The first region uses a work function optimized for threshold voltage control over the active region, while the second regions use different work functions to control depletion layers over isolation regions. This parameter differentiation is achieved through selective deposition or doping processes that can be integrated into existing manufacturing flows.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The gate electrode is constructed as a composite structure with multiple material regions having different work functions. This may involve using different metal layers, alloys, or doped semiconductor materials in different gate regions. The composite structure enables simultaneous optimization of threshold voltage control and depletion layer management, resolving the manufacturing complexity issue through material science rather than process complexity.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS20260020315A1Transistor with modified gate structure

Publication Date: 2026.01.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

The gate electrode of a transistor includes at least one region with a p-type work function and at least one region with an n-type work function. The regions are located over corners formed between isolation regions and an active region. The double hump effect is reduced, which provides higher operational frequencies.