The present disclosure provides a method for fabricating semiconductor devices. The method includes providing a substrate with a gate electrode film on the substrate and a gate electrode pattern film on the gate electrode film; forming at least one pattern layer on the gate electrode pattern film; and using the at least one pattern layer as the etch mask to etch portions of the gate electrode pattern film to expose portions of the gate electrode film and form a gate electrode pattern layer on the gate electrode film, the gate electrode pattern layer including a hard mask layer and a silicon layer, and sidewalls of the silicon layer in a direction perpendicular to a first direction having a first poly line width roughness. The method also includes performing an etch-repairing treatment on the sidewalls of the silicon layer in the direction perpendicular to the first direction.