SOI全名为Silicon On Insulator，是指硅晶体管结构在绝缘体之上的意思，原理就是在硅晶体管之间，加入绝缘体物质，可使两者之间的寄生电容比原来的少上一倍。优点是可以较易提升时脉，并减少电流漏电成为省电的IC，在制程上还可以省略部分光罩以节省成本，因此不论在制程上或是电路上都有其优势。此外，在SOI wafer本身基板的阻值的部分也会影响到组件的表现，因此后来也有公司在基板上进行阻值的调整，达到RF组件特性的提升。原本应通过交换器的电子，有些会钻入硅中造成浪费；SOI可防止电子流失，与补强一些原本Bulk wafer中CMOS组件的缺点。摩托罗拉宣称中央处理器可因此提升时脉20%，并减低耗电30%。除此之外，还可以减少一些有害的电气效应。还有一点，可以说是很多超频玩家所感兴趣的，那就是它的工作温度可高达300°C，减少过热的问题。

Silicon on insulator (SOI) technology refers to the use of a layered silicon–insulator–silicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance, thereby improving performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, typically silicon dioxide or sapphire (these types of devices are called silicon on sapphire, or SOS). The choice of insulator depends largely on intended application, with sapphire being used for high-performance radio frequency (RF) and radiation-sensitive applications, and silicon dioxide for diminished short channel effects in microelectronics devices. The insulating layer and topmost silicon layer also vary widely with application.