DEVICE WAFER PROCESSING METHOD

A device wafer processing method includes a protective film forming step of forming a protective film that covers a face side of a device wafer, a mask forming step of, after the protective film forming step is carried out, applying a laser beam along streets and forming, in the protective film, a mask that has grooves extending along the streets, a device layer plasma etching step of, after the mask forming step is carried out, performing plasma etching on a device layer of the device wafer by device layer gas through the mask, and a base member plasma etching step of, after the device layer plasma etching step is carried out, performing plasma etching on the base member by base member gas through the mask.