A semiconductor device includes a substrate having a memory region and a peripheral region defined thereon, wherein the peripheral region comprises at least one transistor, the memory region comprises a plurality of memory cells, each memory cell comprises at least one gate structure and a capacitor structure, a mask layer disposed on the capacitor structure in the memory region, and a dielectric layer disposed on the substrate within the peripheral region, wherein a top surface of the dielectric layer is aligned with a top surface of the mask layer.