By varying the incident laser wavelength, the intrinsic Raman spectrum of porous silicon formed on nondegeneratep‐type silicon is identified and used to determine the dependence of the average pore size and porosity on the depth of the porous silicon layer. It is found that with increasing layer depth, the average pore size and porosity decreases, which is contrary to that of porous silicon formed on degeneraten‐type silicon. This may indicate a different formation mechanism for these two types of porous silicon.