Silicon Substrate

A silicon substrate has area-selectively formed porous silicon in which porosity, pore size, and pore size distribution of a porous silicon region and a shape of the porous silicon are controlled. In a silicon forming method of immersing the silicon substrate coated with a mask layer having an opening area into a solution to which forming current is applied, and anodically forming a part of the silicon substrate from the opening area of the mask layer so as to form a porous silicon area in the silicon substrate, the forming current is increased according to degree of growth of the porous silicon such that the interface current density between a growing end part of the porous silicon and silicon substrate in the anodizing process may be substantially kept at constant.