Integrated Bipolar-MOSFET Transistor Structure for High Impedance and Current
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Solution Overview
Problem
Current transistor structures fail to simultaneously achieve high input impedance and high current capability without requiring a large integration area, which is necessary for applications like phase change memory cells and other driving circuits.
Innovation Solution
An integrated transistor device is designed with a bipolar transistor and a MOSFET formed in contiguous positions, sharing a common base structure and insulated-gate region, allowing for high input impedance and current conduction capability in a compact structure compatible with standard CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a bipolar transistor with large area is used as selection element, then current driving capability is improved, but input impedance deteriorates
Solution Approach 1:
The patent combines a bipolar transistor and a MOSFET into a single integrated transistor device where the bipolar transistor provides high current driving capability through its collector-emitter path, while the MOSFET provides high input impedance through its insulated gate structure. The two transistor types are merged such that they share common regions (substrate, base/drain region) but maintain distinct functional paths, allowing simultaneous achievement of both high current capability and high input impedance that cannot be obtained with either transistor type alone.
2Reliability
If separate bipolar transistor and MOSFET are used to achieve both high current capability and high input impedance, then functional requirements are met, but integration area increases
Solution Approach 1:
The bipolar transistor and MOSFET are merged into a single integrated device structure where they share common regions including the substrate and the base/drain region. This merging allows both transistors to be implemented within a compact area rather than requiring separate discrete devices, thus meeting both functional requirements (high current capability from bipolar, high input impedance from MOSFET) while minimizing integration area.
Solution Approach 2:
The integrated transistor device performs multiple functions simultaneously: the bipolar transistor portion handles high current driving through the collector-emitter path, the MOSFET portion provides high input impedance through the insulated gate, and both share common structural elements (substrate, base/drain region) to reduce overall device area. This multi-functionality within a single device structure resolves the area contradiction.
3Reliability
If a compact transistor structure is used, then integration area is reduced, but achieving both high input impedance and high current capability becomes difficult
Solution Approach 1:
The patent merges bipolar and MOSFET structures into a single compact device with shared regions (substrate, base/drain region) to achieve both high current capability and high input impedance in a small area. The merging creates a unified structure where the bipolar collector-emitter path and MOSFET gate-channel path coexist within the same physical footprint, reducing integration area while maintaining both functional characteristics.
Solution Approach 2:
The integrated transistor device employs a nested structure where the MOSFET channel region is formed within the bipolar base region, and the source/drain regions are positioned adjacent to the bipolar emitter and collector. This nesting arrangement allows both transistor functions to be embedded within each other's structural footprint, achieving compact integration without excessive structural complexity.
Data Source
AI summary
An integrated transistor device is formed in a chip of semiconductor material having an electrical-insulation region delimiting an active area accommodating a bipolar transistor of vertical type and a MOSFET of planar type, contiguous to one another. The active area accommodates a collector region; a bipolar base region contiguous to the collector region; an emitter region within the bipolar base region; a source region, arranged at a distance from the bipolar base region; a drain region; a channel region arranged between the source region and the drain region; and a well region. The drain region and the bipolar base region are contiguous and form a common base structure shared by the bipolar transistor and the MOSFET. Thereby, the integrated transistor device has a high input impedance and is capable of driving high currents, while only requiring a small integration area.