SiO2 thin films were successfully deposited by plasma-enhanced atomic layer deposition (PEALD) using a divalent Si precursor (N,N'-tert-butyl-1,1-dimethylethylenediamine silylene) and oxygen plasma as reactants. The growth behavior of SiOx exhibited the typical self-limiting surface reaction depending on the precursor dose and plasma time over a wide deposition temperature range (80-200 degrees C) of the ALD window, showing a growth rate of about 1 angstrom/cycle. The properties of the SiOx thin films were investigated using various analysis tools. The films exhibited a refractive index value of about 1.45-1.5, which corresponds to the refractive index of SiO2. The dielectric property was evaluated, and a high breakdown voltage and low leakage current was observed owing to the absence of carbon or nitrogen impurities. The density functional theory (DFT) was used to determine the growth mechanism during the ALD growth sequence.