A silicon on insulator (SOI) device includes a wafer and a trap-rich layer. The wafer includes a top silicon layer disposed on a buried oxide layer. The trap-rich layer having nano-dots and an oxide layer are stacked on a high resistivity substrate sequentially, wherein the oxide layer is bonded with the buried oxide layer. Or, a silicon on insulator (SOI) device includes a wafer and a high resistivity substrate. The wafer includes a top silicon layer disposed on a buried oxide layer. The high resistivity substrate is bonded with the buried oxide layer, wherein a positive fixed charge layer is induced at a surface of the buried oxide layer contacting the high resistivity substrate, and a doped negative charge layer is right next to the positive fixed charge layer. The present invention also provides a method of forming said silicon on insulator (SOI) device.