In this paper, we study the effect of Hg lamp ultraviolet (UV) irradiation on the physical properties and wet etch resistance of perhydro-polysilazane-based inorganic spin-on-glass (PSZ-SOG) film. Superior film qualities include smaller volumetric shrinkage, better thickness uniformity, and minor tensile stress variation of the SOG film can be obtained by applying UV curing with higher temperature, stronger irradiation power, and longer exposure time procedure. In addition, better PSZ-SOG conversion efficiency is showed based on FT-IR and SIMS analysis; results in the higher wet etch amount. The better convertibility of PSZ-SOG film comes mainly from the efficient energy of UV photon (3.88 -5.64 eV) irradiation; it can trigger the Si-H (4.07 eV) and Si-N (3.68 eV) bonds dissociation and promote the conversion to Si-O bonds at O 2 or H 2 O environment. As to the wet etch resistance inside the trench, the samples with UV irradiation exhibit preferable performance. It can attribute to the more uniform and smaller stress change of oxide film formation as compared with the samples without UV curing. Therefore, the new promising solution of UV irradiation provides better depth profile of PSZ conversion and uniform oxide film at STI area without extra thermal budget.