A method of forming a material film includes providing a non-photosensitive mask on a substrate to expose a partial region of the substrate, forming a material film on the partial region of the substrate using a sputtering process, removing the non-photosensitive mask, and heat-treating the substrate and the material film from which the non-photosensitive mask is removed under a first gas atmosphere. The material film includes a transition metal and a chalcogen element. The sputtering process may include an RF magnetron sputtering process. The heat treatment may be performed at a higher temperature than a temperature of the forming the material film.