A method of an interfacial oxide layer formation comprises a plurality of steps. The step (S1) is to remove a native oxide layer from a surface of a substrate; the step (S2) is to form an oxide layer on a surface of a substrate by piranha solution (SPM); the step (S3) is to cleaning a surface of the oxide layer by standard clean 1 (SC1), and the step (S4) is to etch he oxide layer by a solution comprising diluted hydrogen fluoride (dHF) and ozonized pure water (DIO3).