PURPOSE: A method for depositing a cyclic thin film is provided to obtain a high step coverage by forming an insulation layer with silicon under a plasma atmosphere. CONSTITUTION: Silicon is deposited on a substrate by injecting a silicon precursor into a chamber loading the substrate(S210). A non-reactive silicon precursor and a by-product are removed in the chamber(S220). The deposited silicon is changed into an insulation layer with silicon by supplying first reactive gas to the chamber(S230). The non-reactive first reactive gas and by-product are repeatedly removed in the chamber. The insulation layer with silicon becomes dense by supplying a plasma atmosphere to the chamber(S300).
