The Sidewall Spacer (SWS) Pad Oxide deposition serves as a critical buffer and etch-stop layer in the formation of the self-aligned transistor spacer structure T2.Positioned immediately after the lightly doped drain (LDD) implantation and subsequent resist stripping, this step prepares the wafer for the main SWS silicon nitride deposition P4.The primary integration logic for inserting a pad oxide before the main nitride spacer is two-fold: it protects the underlying crystalline silicon and gate