Semiconductor nanostructures have got considerable attention since they are building blocks of future nanoscale devices for electronics and photonics. Nowadays, nanostructures are the most investigated object in solid-state physics, especially concerning quantum confinement effect in quantum dots, quantum wires and quantum wells. In the case of nanosize structures the energy band diagram of semiconductor is strongly changed. This leads to crucial change of the semiconductor properties such as: electroconductivity (due to the change of free charge carrier concentration and electrons and holes mobility); optical parameters (absorption coefficient, reflectivity index, radiative recombination efficiency); mechanical and heating properties. The aim of this work is to study the mechanism of nanohills growth in SiGe/Si structure by laser radiation. The mechanism of nanohills growth in SiGe/Si structure by laser radiation is proposed by following model: irradiation of SiGe/Si heterostructure by Nd:YAG laser initiates Ge atoms drift to the irradiated surface due to gradient of temperature - Thermogradient effect. This process is characterized by positive feedback: after every laser pulse gradient of temperature increases due to increase of Ge atoms concentration at the irradiated surface and new Ge phase formation at the end of the process. Ge atoms are localized at the surface of Si like a thin film. Self-assembly of nanostructure on the irradiated surface takes place due to growth of nanostructure by Stransky- Krastanov’ mode.