​$$\text{In the fabrication of a semiconductor device using the Dual-well Process or Twin-tub Process, the first step involves depositing a thin layer of SiO}_2 \text{ on a p-substrate surfaced with a lightly doped p-epitaxial layer. What is the purpose of the thin SiO}_2 \text{ layer deposited in the first step of the Dual-well Process or Twin-tub Process?}$$​​

Correct option is A

In the Twin-Tub/Dual-Well Process, the initial thin SiO₂ layer on the epitaxial layer serves as a pad oxide, providing protection and a buffer during subsequent steps like nitride deposition for well formation, preventing direct contact/damage to the sensitive epitaxial layer during etching and ion implantation for N-wells and P-wells before the actual gate oxide is grown later for transistors.