Dual Work Function Buried Gate Transistor for Leakage Reduction
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Solution Overview
Problem
Buried gate transistors face a trade-off between reducing gate-induced drain leakage (GIDL) and maintaining current drivability due to the high work function of metal gate electrodes, which increases resistance when the gate height is lowered.
Innovation Solution
A dual work function buried gate electrode structure is implemented, comprising a high work function first electrode, a low work function liner electrode that overlaps with source and drain regions, and a low resistance second electrode, with a barrier layer to prevent reaction and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the height of the buried metal gate electrode is lowered to reduce overlap area with source/drain regions, then gate-induced drain leakage (GIDL) is reduced, but gate resistance increases and current drivability is degraded
Solution Approach 1:
The gate electrode is divided into two regions with different work functions: a first region with high work function (4.5-5.5 eV) positioned away from source/drain regions to reduce GIDL, and a second region with low work function (3.5-4.5 eV) positioned overlapping with source/drain regions to reduce gate resistance. This local differentiation of material properties resolves the contradiction by optimizing each region's function independently.
Solution Approach 2:
The gate electrode is segmented into multiple portions with different work functions along its length. The gate electrode includes a first gate electrode portion and a second gate electrode portion, each with distinct work function characteristics, allowing simultaneous optimization of GIDL reduction and current drivability through spatial segmentation of functional properties.
Data Source
AI summary
A transistor having a source region and a drain region which are separately formed in a substrate, a trench which is defined in the substrate between the source region and the drain region, and a gate electrode which is formed in the trench. The gate electrode includes a first electrode buried over a bottom of the trench; a second electrode formed over the first electrode; and a liner electrode having an interface part which is positioned between the first electrode and the second electrode and a side part, which is positioned on sidewalls of the second electrode and overlaps with the source region and the drain region.