By removing and re-growing the oxide layer, we can then repeat the previous lithography, etch and strip processes with a different mask to create a window opening in the oxide where we want to build the transistor's gate region.

The gate is a conductive layer which is separated from the bulk silicon by a thin gate oxide. A positive electrical charge on the gate will create an opposite negative field in the surface of the silicon. This negative field essentially creates a conductive channel between the source and the drain, letting current flow between them.

The gate oxide needs to be thin since the electrical field must transfer across this insulator. Typically, this is made by depositing silicon nitride film via a Chemical Vapor Deposition process (CVD).

The gate itself is either made of polysilicon or a metal. Polysilicon is deposited by a Physical Vapor Deposition (PVD) process, often known as "sputtering".

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