The method includes following steps. First, the semiconductor substrate with the dielectric layer on it is provided. Then, the photoresistive layer is formed and limited on the dielectric layer. Next, the etching procedure is carried out in order to form the groove on the dielectric layer. The etchant used in the etching procedure contains the mixed gas including at least C4F6 or CH2F2 for example C4F6/CH2F2/Ar/O2, C4F6/CH2F2Ar/O2/CF4, mixed gas including at least C4F6 or CH2F2 for example C4F6/CH2F2/Ar/O2, C4F6/CH2F2Ar/O2/CF4, C4F6/CH2F2/Ar/O2/C2F6 etc. Thus, the etching selection ratio between the dielectric layer and the photoresistive layer is increased and the etching capability of the etchant is enhanced. Finally, the photoresistive layer is removed to form the contact window or the dielctric hole. |