Fluorine-doped tin oxide (FTO) thin films on a polyethylene terephthalate (PET) as a flexible transparent heater was prepared by electron cyclotron resonance - metal organic chemical vapor deposition (ECR-MOCVD). Under plasma environment, the films were fabricated by supplying tetra-methyl tin (TMT) as precursors for tin, sulfur-hexafluoride (SF6) as precursor for fluorine atoms, oxygen and hydrogen for about 15 min deposition. The result shows that the FTO films have nanocrystalline structure with a grain size of 30-60 nm, a thickness of 300 nm and transmittance over 85 %. The observed lowest sheet resistance of 253 Ω was found in our experimental range. We conclude that the optimum content of fluorine doping plays an important role to affect the structural, electrical, optical and thermal properties of the FTO thin films as transparent materials.