Gate Trench Electrode Layout to Reduce GIDL in Memory Cells
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Solution Overview
Problem
As semiconductor memory devices become increasingly high-integrated, they face challenges in minimizing the short channel effect and improving reliability and performance, particularly in buried channel array transistors where gate-induced drain leakage (GIDL) is a concern due to the integration of both main and pass gate electrodes.
Innovation Solution
The semiconductor device incorporates a gate trench with a main gate electrode and a pass gate electrode, where the pass gate electrode is positioned lower than the main gate electrode, and a support structure is used to fill the upper part of the trench, reducing overlap areas and GIDL, while a gate insulating film extends along the sidewalls and bottom surfaces of both electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a gate trench extends across both the active region and the isolation film to include both main and pass gate electrodes, then the device integration is improved, but gate-induced drain leakage (GIDL) increases and reliability deteriorates
Solution Approach 1:
The gate trench is segmented into two distinct portions: a first trench in the active region containing the main gate electrode, and a second trench in the isolation film containing the pass gate electrode. This segmentation allows the main and pass gates to be spatially separated, reducing their overlap area and thereby minimizing gate-induced drain leakage while maintaining high device integration.
2Productivity
If the gate trench has a large aspect ratio to achieve high integration, then device integration is improved, but manufacturing precision becomes more difficult
Solution Approach 1:
The continuous gate trench is divided into separate first and second trenches with different depths and locations. The first trench extends into the active region while the second trench is formed in the isolation film at a different depth level. This segmentation reduces the overall aspect ratio requirements for each individual trench, making fabrication more precise and controllable while achieving high device integration.
Solution Approach 2:
The gate structure is extended into the vertical dimension by forming trenches at different depths: the main gate electrode is positioned at a first depth in the active region, while the pass gate electrode is positioned at a second depth in the isolation film. This three-dimensional arrangement reduces the horizontal overlap area and eases the aspect ratio constraints for each trench, improving manufacturability.
3Reliability
If the pass gate electrode is positioned lower than the main gate electrode to reduce overlap area, then gate-induced drain leakage is reduced, but the trench structure requires support to maintain stability
Solution Approach 1:
A fill material is introduced as an intermediary substance to fill the upper portion of the second trench above the pass gate electrode. This fill material provides mechanical support and structural stability to the trench configuration, preventing collapse or deformation while allowing the pass gate electrode to maintain its lower position for reduced overlap area and minimized gate-induced drain leakage.
Data Source
AI summary
A semiconductor device includes an active region in a substrate, an isolation film defining the active region in the substrate, a gate trench extending across the active region and the isolation film and including a first trench in the active region and a second trench in the isolation film, a gate electrode including a main gate electrode and a pass gate electrode, the main gate electrode filling a lower part of the first trench, and the pass gate electrode filling a lower part of the second trench, a support structure on the pass gate electrode, the support structure filling an upper part of the second trench, a gate insulating film interposed between the isolation film and the pass gate electrode and between the support structure and the pass gate electrode.