SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME

A semiconductor device having a semiconductor substrate, a BOX film on the semiconductor substrate, a semiconductor layer on the BOX film, a first trench penetrated through the semiconductor layer and reached to the first insulating film, a first insulating film covering a side surface of the first trench and in contact with an upper surface of the BOX film at a bottom of the first trench, a second trench formed at the bottom of the first trench such that the second trench penetrates through the first insulating film and reached in the BOX film, a second insulating film filled in the first trench and the second trench. A bottom surface of the second trench is located in the BOX film below an interface between the semiconductor layer and the BOX film, and a void is located in the second insulating film at the same height the interface.