PURPOSE: To form a fine pattern by a simple process, by transforming a metal thin film formed at a desired position on material to be etched into fine particles by heating.

CONSTITUTION: A metal thin film 15 is formed at a desired position on material 10 to be etched, and a mask is constituted by transforming the film 15 into fine particles by heating. When an Au thin film is used and the thickness is set as 5nm, fine particles several tens of nm in outer diameter are obtained at a heating temperature of 300°C or higher independently from the heating time, and the interval between fine particles also becomes smaller than or equal to several tens of nm. When the film thickness is 10nm, the fine particles 100-200nm in outer diameter are obtained at a heating temperature of 450°C. When the film is 20nm, the fine particles 0.5μm in outer diameter are obtained at a heating temperature of 450°C. The interval becomes nearly equal to the outer diameter. Hence the dimension of the fine particles to be obtained as the mask can be easily and surely controlled by the thickness of the metal thin film and the heating temperature. Thereby a fine pattern can be formed by a simple process.