Compensated Isolated P-Well DENMOS Transistors

The patent combines the high voltage DENMOS transistor formation with the baseline CMOS process flow by utilizing the existing n-well structure. The deep n-well serves dual purposes: as the substrate for both low voltage NMOS transistors and as the drift region for high voltage DENMOS transistors. This merging eliminates the need for separate high voltage well formation processes and reduces the number of photolithography steps required.

The n-well structure is designed to serve multiple functions simultaneously: it acts as the well for low voltage NMOS transistors, provides the drift region for high voltage DENMOS transistors, and serves as the isolation structure. The gate dielectric thickness is optimized to handle both low voltage operation and high voltage stress, making it a universal solution for both transistor types.

The patent merges the high voltage and low voltage transistor formation processes into a single integrated flow. The same n-well implantation and gate dielectric deposition steps serve both low voltage NMOS and high voltage DENMOS transistor formation, eliminating the need for separate processing lines and reducing manufacturing costs.

The baseline CMOS process flow is designed to automatically provide the necessary structures for high voltage DENMOS transistors without requiring additional dedicated steps. The n-well formation and gate dielectric deposition processes self-configure to support both low and high voltage devices, reducing the need for additional manufacturing resources.

The patent extracts the high voltage switching function into a dedicated DENMOS transistor structure that is physically isolated from low voltage circuits. The deep n-well acts as an isolation barrier, extracting and containing the high voltage effects within a specific region, preventing them from affecting adjacent low voltage circuits.

The deep n-well serves as an intermediary structure between high voltage and low voltage regions. It provides electrical isolation and acts as a buffer that prevents voltage disturbances from propagating from the high voltage DENMOS transistor to adjacent low voltage circuits, while still allowing the high voltage switching function to operate effectively.

The patent combines multiple process steps into fewer operations. The n-well formation process simultaneously creates the structure needed for both low voltage NMOS and high voltage DENMOS transistors. The gate dielectric deposition and photolithography steps are consolidated to serve both transistor types, reducing the total number of manufacturing cycles required.

The n-well structure is formed in advance during the baseline CMOS process flow, before the final transistor type assignment. This preliminary action allows the same pre-formed structure to be used for both low and high voltage devices, eliminating the need for additional well formation steps later in the process and reducing overall manufacturing cycle time.