An object of the present invention is to provide a method of forming fine particles on a substrate in which reoxidization of reduced fine particles is suppressed. Reduced fine particles (FeO fine particles) are formed by embedding metal oxide fine particles (Fe.sub.2O.sub.3 fine particles) fixed on a p type silicon semiconductor substrate into a silicon oxidized film, and carrying out a heat treatment in a reducing gas atmosphere. Presence of the silicon oxidized film enables suppression of reoxidization of the reduced fine particles (FeO fine particles) due to exposure to the ambient air.