A wafer process material is prepared which has a plurality of semiconductor formation regions of different planar sizes, each including a low dielectric constant film/wiring line stack structure component. A laser beam is applied onto a dicing street of the necessary semiconductor formation region and onto its straight extension in order to remove partial areas of the low dielectric constant film/wiring line stack structure components of the necessary semiconductor formation region and the unnecessary semiconductor formation region so that first groove and the second groove are formed. A protective film is formed in the second groove formed in the unnecessary semiconductor formation region and on the low dielectric constant film/wiring line stack structure component. An upper wiring line and a sealing film are formed on the protective film, and a semiconductor wafer is cut along the dicing street.