Optical device and method of manufacturing the same

An optical device forms a refractive index distribution for exhibiting a certain phase delay profile with respect to light in a visible light wavelength, and includes a nanopattern layer including a crystalline compound having a refractive index greater than 3 with respect to the light in the visible light wavelength band and a height equal to or less than 2 μm. The nanopattern layer may include the crystalline compound grown according to a selective epitaxial growth method, and accordingly, may have a height beneficial for a manufacturing process. Thus, the efficiency of the optical device may be improved.