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 film stack disposed on a substrate without planarization. The method includes forming a hardmask on a top surface of a film stack. Forming a mask material on a portion of the top surface and a portion of the hardmask. Etching the top surface. Trimming the mask. Etching the top surface again. Trimming the mask a second time. Etching the top surface yet again and then stripping the mask material.