Method for forming semiconductor device structure

A method for forming a semiconductor device structure is provided. The semiconductor device structure includes forming a film over a substrate. The semiconductor device structure includes forming a first mask layer over the film. The semiconductor device structure includes forming a second mask layer over the first mask layer. The second mask layer exposes a first portion of the first mask layer. The semiconductor device structure includes performing a plasma etching and deposition process to remove the first portion of the first mask layer and to form a protection layer over a first sidewall of the second mask layer. The first mask layer exposes a second portion of the film after the plasma etching and deposition process. The semiconductor device structure includes removing the second portion using the first mask layer and the second mask layer as an etching mask.