The semiconductor device 1 has a semiconductor chip 10 (first semiconductor chip) and a semiconductor chip 20 (second semiconductor chip). The semiconductor chip 20 is formed on the semiconductor chip 10. The semiconductor chip 20 is constituted by comprising a semiconductor substrate 22. The semiconductor substrate 22, which is an SOI substrate, is constituted by comprising an insulating layer 34, and a silicon layer 36, which is provided on the insulating layer 34, including a circuit forming region A1. The insulating layer 34 functions as a protective film (a first protective film) covering a lower face (a face opposite to the semiconductor chip 10) of the circuit forming region A1. A protective film 38 (a second protective film) is provided on the semiconductor substrate 22. The protective film 38 covers a side face of the circuit forming region A1.