Fin Channel Recess Gate Structure for DRAM Scaling
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Solution Overview
Problem
Conventional semiconductor devices experience increased channel resistance and degraded refresh characteristics due to enhanced electric fields in source/drain regions, leading to reduced read/write speed and driving current when channel length is decreased.
Innovation Solution
A semiconductor device is fabricated using an island-shaped recess gate mask to form a recess channel region and a Fin channel region at the lower part of the recess, with a gate insulating film and gate electrode filling the Fin channel region, reducing channel resistance and improving refresh characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If channel length is decreased to improve device scaling, then device density is improved, but channel resistance increases and refresh characteristic degrades
Solution Approach 1:
The patent introduces a Fin channel region that extends vertically into the substrate, transforming the channel structure from a planar 2D configuration to a 3D vertical configuration. This dimensional change allows the channel to provide additional conduction paths without increasing the lateral footprint, thereby maintaining device density while reducing channel resistance and improving refresh characteristics through enhanced current flow capability.
Solution Approach 2:
The Fin channel region is nested within the recess structure, with the gate electrode wrapping around the Fin channel region. This nested configuration allows the gate to control the channel current from multiple directions (top and sidewalls), providing superior electrostatic control and reducing short-channel effects while maintaining compact device dimensions.
2Reliability
If ion concentration in cell channel region is increased to maintain threshold voltage, then threshold voltage is maintained, but electric field in source/drain regions is enhanced causing leakage current increase
Solution Approach 1:
The patent implements localized doping regions with different ion concentrations in specific areas: high ion concentration in the Fin channel region to maintain threshold voltage, and lower ion concentration in the source/drain regions to reduce leakage current. This spatial differentiation of doping profiles allows simultaneous optimization of threshold voltage control and leakage reduction.
Solution Approach 2:
By extending the channel into the vertical dimension through the Fin structure, the patent reduces the lateral electric field strength in source/drain regions while maintaining adequate field control in the channel. The vertical orientation distributes the electric field more favorably, reducing tunneling leakage without compromising threshold voltage control.
3Reliability
If width of horizontal channel region is increased to reduce channel resistance, then channel resistance is reduced, but device area increases
Solution Approach 1:
The patent resolves this contradiction by extending the channel in the vertical dimension rather than increasing lateral width. The Fin channel region provides additional conduction cross-section area through its vertical extent, reducing channel resistance without increasing the device footprint. The gate electrode wraps around the Fin structure to provide control over this vertically extended channel.
Data Source
AI summary
The semiconductor device includes an active region, a recess, a Fin channel region, a gate insulating film, and a gate electrode. The active region is defined by a device isolation structure formed in a semiconductor substrate. The recess is formed by etching the active region and its neighboring device isolation structure using an island shaped recess gate mask as an etching mask. The Fin channel region is formed on the semiconductor substrate at a lower part of the recess. The gate insulating film is formed over the active region including the Fin channel region and the recess. The gate electrode is formed over the gate insulating film to fill up the Fin channel region and the recess.