Embodiments herein describe a sub-micron 3D diffractive optics element and a method for forming the sub-micron 3D diffractive optics element. In a first embodiment, a method is provided for forming a sub-micron 3D diffractive optics element on a substrate without planarization. The method includes depositing a material stack to be patterned on a substrate, depositing and patterning a thick mask material on a portion of the material stack, etching the material stack down one level, trimming a side portion of the thick mask material, etching the material stack down one more level, repeating trim and etch steps above ‘n’ times, and stripping the thick mask material from the material stack.