Transmission electron microscopy, scanning electron microscopy, and x‐ray analysis are used to study the structure of evaporated and pyrolytic silicon films (less than 1μ thick) deposited at or heat-treated in the temperature range of 500°–1040°C. It is established that the thin silicon film subjects of this investigation can have three different morphologies: pseudoamorphous, equiaxed grains, or dendritic. These are attributed to be functions of deposition temperature for pyrolytic films and heat-treatment temperature for evaporated films. The nucleation phenomena of pyrolytic silicon thin films as a function of time spent in N2 prior to silicon deposition is investigated. Also the analysis of possible silicon film impurities is performed.