Epitaxial Wafer has a single crystal silicon layer on top of single crystal silicon substrate (Polished Wafer). They both have the same crystal structure, but Epitaxial layer differs in physical properties such as dropping, band gap and permittivity properties, yielding less defect density than the substrate. Therefore, it has superior structural and electrical properties to the original Polished Wafer, making it possible to improve performance on manufacturing extensive semiconductor devices.