Abstract: A method for forming a titanium dioxide layer is disclosed. The method includes the steps of providing a titanium-containing material, adding hydrogen chloride and nitric acid to the titanium-containing material to form a mixture, and exposing the device to the mixture to form the titanium dioxide layer thereon. Not only can the refractive index of the titanium dioxide layer formed by this method be increased, but also its growth rate and stability will be enhanced to be applied in the production line. Such a method can be applied for forming a titanium dioxide layer on a semiconductor device, a silicon substrate, an integrated circuit, a photoelectric device, etc.