Abstract: Disclosed is an etching method for a semiconductor device. The protecting layer, such as the hydrocarbon layer or the hydrocarbon layer containing phosphorous, is formed on the photoresist layer by using the precursor gas containing no fluorine. Therefore, the etching process enabling the thin photoresist to have a high selectivity can be performed, thereby improving the etching efficiency. The method includes the steps of placing a semiconductor substrate in a chamber, in which a material layer is formed on the semiconductor substrate and a photoresist layer is formed on the material layer, forming a hydrocarbon layer on the photoresist layer by introducing precursor gas containing no fluorine into the chamber and etching an etching target material by introducing etching gas into the chamber.