Thin film element, semiconductor device, and method for manufacturing the same

A method for manufacturing a semiconductor device, the method comprising the steps of:

• forming a semiconductor film over a substrate;
• forming a conductive film over the semiconductor film;
• forming a mask layer over the conductive film;
• etching the semiconductor film and the conductive film consecutively by dry etching using the mask layer as a mask after forming the mask layer;
• forming an insulating film over the mask layer after etching the semiconductor film and the conductive film consecutively;
• etching the insulating film by anisotropic etching to form a sidewall which covers a side surface of the semiconductor film and to expose the mask layer after forming the insulating film;
• after the anisotropic etching forming a source electrode layer and a drain electrode layer by etching the conductive film whose side surface is covered by the sidewall;
• and
• forming a pixel electrode layer electrically connected to one of the source electrode layer and the drain electrode layer.