In the case of forming a thin film semiconductor device by polishing a wafer, the rear surface of each chip must have been separately processed independently by being divided into chips. In this invention, the front surface of a wafer (2a) is bonded on a rigid supporting body (5) through a bonding layer (6), in a status where a groove section (4) is formed on the front surface of the wafer (2a) by half dicing. Then, after polishing the rear surface of the wafer (2a) and dividing the wafer into each chip (2b), rear surface processing, including heat treatment for forming a rear surface electrode (9a) and the like, is performed without separating the chip (2b) from the supporting body (5).