A semiconductor device with voids within a silicon-on-insulator (SOI) structure and a method of forming the semiconductor device are provided. Voids are formed within a Buried Oxide layer (BOX layer) of the silicon-on-insulator (SOI) semiconductor to enhance a performance index of an RF-SOI switch. The semiconductor device with voids within a silicon-on-insulator (SOI) structure includes a semiconductor substrate; an insulating layer disposed on the substrate; a silicon-on-insulator (SOI) layer disposed on the insulating layer; a device isolation layer and an active area disposed within the SOI layer; one or more voids disposed within the insulating layer; and a sealing insulating sealing an opening of the void.