Abstract: A package base structure for packaging a light-emitting element and a related manufacturing process are provided. The package base structure includes a semiconductor substrate having a top surface, a receiving space in the top surface and defined by slant surfaces, and a micro diffractive optical element on one of the slant surfaces. To produce the package base structure, a first etching mask with a first etching window is formed on the top surface. The etching window has a sidewall oriented at a bias angle with respect to a specific equivalent crystallographic orientation of the semiconductor substrate. Then, a selective anisotropic etching procedure is performed through the first etching window to form the slant surfaces on the semiconductor substrate. Afterwards, the micro diffractive optical element is formed on the slant surface for collimating or focusing a light beam emitted from the light-emitting element.