Transistor Gate Extending into Recessed Semiconductor Base
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Solution Overview
Problem
Conventional transistor configurations face scalability limits due to short-channel effects such as drain-induced barrier lowering and hot-carrier degradation as channel regions become shorter, hindering the development of highly integrated assemblies with increased integration density and reduced footprint.
Innovation Solution
The design includes a transistor configuration with a gate material extending into a recess in a semiconductor base, featuring a ledge and insulative spacers, which alleviates short-channel effects by lengthening the channel region and reducing hot-carrier degradation, particularly when the recessed segment is directly against the drain region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional transistor configurations are used to increase integration density, then the footprint of integrated components is reduced, but short-channel effects such as drain-induced barrier lowering and hot-carrier degradation worsen
Solution Approach 1:
The gate structure transitions from a planar two-dimensional configuration to a three-dimensional configuration by extending the gate into a recessed region beneath the semiconductor base surface. This vertical extension into the third dimension allows the channel length to be effectively increased without increasing the lateral footprint, thereby maintaining high integration density while improving transistor performance by reducing short-channel effects
Solution Approach 2:
The gate structure is nested within the recessed region of the semiconductor base, with the gate material positioned within a vertically-defined cavity. This nesting approach allows the gate to occupy space beneath the base surface rather than only at the surface level, enabling longer channel lengths to be achieved within the same lateral footprint and thus resolving the contradiction between miniaturization and performance
2Productivity
If channel regions are made shorter to increase integration density, then the footprint is reduced, but short-channel effects such as drain-induced barrier lowering increase
Solution Approach 1:
By extending the gate vertically into the recessed region, the effective channel length is increased in the vertical dimension while the lateral dimensions remain compact. This dimensional transition allows high integration density to be achieved without sacrificing channel length, thereby preventing drain-induced barrier lowering and other short-channel effects
3Area of moving object
If channel regions are made shorter to reduce footprint, then integration density increases, but hot-carrier degradation worsens
Solution Approach 1:
The vertical extension of the gate into the recessed region increases the effective channel length without increasing the lateral footprint. This longer channel length reduces the electric field strength and hot-carrier generation, thereby improving transistor reliability and lifetime while maintaining compact device dimensions for high integration density
Data Source
AI summary
Some embodiments include an integrated assembly with a semiconductor base having a horizontally-extending upper surface, and having a recessed region. A transistor gate is supported by the semiconductor base. The transistor gate has a first segment over the horizontally-extending upper surface, and has a second segment over the recessed region. The first segment has a first vertically-extending surface along an outer edge. The second segment has a ledge along an edge of the recessed region. The ledge has an upper surface which is lower than the horizontally-extending upper surface. The second segment has a second vertically-extending surface extending upwardly from an inner portion of the ledge. A first spacer is along the first vertically-extending surface. A second spacer is along the second vertically-extending surface. The second spacer has a bottom edge beneath the horizontally-extending upper surface of the base.