A method of preparing a patterned thin film resistor that is appropriately used in combination with semiconductor devices. The method comprises a thin film forming step comprising forming a thin film of a compound comprising at least one metal on an oxide film such as a silicon oxide film; a masking step comprising covering a desired area of the thin film by an organic material; a patterning step comprising converting to plasma a gas mixture comprising a fluorine compound gas and oxygen, and removing an area of the thin film, that is not covered by the organic material by exposing it to a gas containing activated fluorine by the plasma conversion; and a removing step comprising removing the organic material remaining on the desired area of the thin film.