The pad oxide etch step serves as the final breakthrough process in the contact formation module, removing a thin protective dielectric layer to expose the underlying active silicon or polysilicon gate A1. This step sequentially follows the bulk Pre-Metal Dielectric (PMD) etch and the Contact Etch Stop Layer (CESL) opening (Engineering Practice). Unlike the earlier PMD oxide etch, which is designed for high-rate removal of thick dielectric materials in high aspect ratio structures, the pad oxide