Thin film etching method

A thin film etching method is disclosed, which is used for manufacturing semiconductor device or thin film transistor (TFT) array and through which no undercut may be presented or a good after-etching shape may be achieved with respect to a thin film thus etched. The thin film etching method is performed in a two-stage manner by an etchant and between the two stages a photoresist removing process is inserted where another etchant is used. With execution of the photoresist removing process, the thin film may have an increased contact area with the etchant. As such, any undercut or undesired after-etching shape existed in the thin film etched by the prior art may be eliminated or improved.