Recessed Gate Structure for Transistor Corner Effect
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Solution Overview
Problem
Transistor devices with shallow trench isolation structures face a 'corner effect' issue due to non-uniform doping concentrations at the interface region, leading to a double-hump drain current versus gate voltage curve, reduced threshold voltage, and increased noise, which is difficult to address with existing methods that require additional implants and complex processing.
Innovation Solution
A transistor device with a recessed gate structure is designed, where the gate is cut off at the interface region by forming recess regions on either side, preventing carrier transfer and eliminating the corner effect without the need for additional masking processes, thus maintaining a stable threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a conventional gate structure is used over the interface region, then the device region can be fully utilized, but non-uniform doping concentrations occur leading to corner effect and double-hump IDVG curve
Solution Approach 1:
The gate structure is extracted or removed from the interface region by forming recess regions that laterally extend into the device region. This extraction eliminates the gate's presence at the problematic interface area, preventing the corner effect and non-uniform doping concentrations while maintaining full device region utilization.
Solution Approach 2:
The gate structure is segmented into two distinct regions: a first region over the device region with normal gate coverage, and a second region over the isolation structure with recesses. This segmentation allows the gate to function properly over the device region while avoiding the interface region to prevent doping non-uniformity.
2Reliability
If additional implants are used to address corner effect, then threshold voltage stability can be improved, but processing complexity increases
Solution Approach 1:
The recess regions are formed in the gate structure before the doping process. This preliminary action pre-configures the gate to exclude the interface region from its coverage area, thereby preventing corner effect and ensuring uniform doping concentrations without requiring additional corrective implant steps.
Solution Approach 2:
The design converts the potentially harmful interface region into a beneficial recess area. By intentionally creating recess regions that lateral extend into the device region, the interface area is excluded from gate coverage, transforming what would be a source of non-uniform doping into a feature that ensures doping uniformity and threshold voltage stability.
Data Source
AI summary
A transistor device with a recessed gate structure is provided. In some embodiments, the transistor device comprises a semiconductor substrate comprising a device region surrounded by an isolation structure and a pair of source/drain regions disposed in the device region and laterally spaced apart one from another in a first direction. A gate structure overlies the device region and the isolation structure and arranged between the pair of source/drain regions. The gate structure comprises a pair of recess regions disposed on opposite sides of the device region in a second direction perpendicular to the first direction. A channel region is disposed in the device region underneath the gate structure. The channel region has a channel width extending in the second direction from one of the recess regions to the other one of the recess regions.