The cone-like nanostructure formed on the irradiated surface of semiconductors by Nd:YAG laser possessing the properties of 1D graded band gap has been found. Such properties are explained in the frame of Quantum confinement effect. For explanation of the nature of nanocones’ formation on the irradiated surface of semiconductors, the two-stage model is proposed. The first stage is characterized by formation of a thin strained top layer, due to redistribution of point defects in temperature gradient field induced by laser radiation. The second one is characterised by mechanical plastic deformation of the stained top layer leading to arising of nanocones, due to selective laser absorption. The model is confirmed by “blue shift” of photoluminescence spectrum, “red shift” of LO line in Raman back scattering spectrum and non-monotonous dependence of Si crystal micro-hardness as function of the laser intensity.