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nMOS Enhancement Type Transistors

• p-type silicon substrate is utilized for nMOS enhancement type transistors.
• n-type regions are created to form the active areas of the transistor.

Silicon Dioxide Layer

• A thin layer of silicon dioxide is formed as an insulating layer, crucial for device functionality and isolation.
• It is created using techniques such as thermal oxidation.

Creating Windows in SiO2 Layer

• Photolithography technique is employed to pattern and create openings or windows in the silicon dioxide layer.
• This allows for selective implantation of impurities in specific areas of the substrate.

Impurity Implantation

• Donor impurities, typically phosphorus or arsenic, are implanted into the exposed areas to form n-type regions.
• This doping process enhances the conductivity of the areas, enabling the behavior of nMOS transistors.

Gate Electrode Material

• The gate electrode is commonly formed using polysilicon, which offers good conductivity and compatibility with silicon processes.

Silicon Dioxide Creation Process

• The formation of silicon dioxide is primarily achieved through thermal oxidation, where silicon is exposed to oxygen at elevated temperatures.

Function of n-type Regions

• The n-type regions serve as the source and drain terminals in the nMOS transistor, allowing electrons to flow and enabling switching characteristics.

Gate Electrode Patterning Technique

• The same photolithography technique used for creating windows is applied to pattern the polysilicon layer for the gate electrode.
• This ensures precise shaping and alignment for effective transistor operation.

Transistor Types Formed

• The process described is specifically used to manufacture n-type Metal-Oxide-Semiconductor (nMOS) transistors.