A semiconductor substrate having an integrated circuit die area surrounded by a scribe lane is provided. Within the integrated circuit die area, a first trench isolation region and a second trench isolation region are formed on the semiconductor substrate, wherein the first trench isolation region isolates a first active device region from a second active device region, and the second trench isolation region comprises a plurality of trench dummy features for reducing loading effect. A first gate electrode is formed on the first active device region and a second gate electrode on the second active device region. The first active device region is masked, while the second active device region and the trench dummy features are exposed. An ion implantation process is then performed to implant dopant species into the second active device region.