Patent ID: 7638376

Claim:
A method for forming a substrate contact on a silicon-on-insulator (SOI) wafer, comprising: providing a SOI wafer with a mask layer thereon, wherein the SOI wafer includes an underlying substrate, and a silicon layer overlaying a buried insulating layer; forming an isolation region through the mask layer and the silicon layer, wherein the isolation region is substantially coplanar with a top surface of the mask layer; forming a contact opening through a central portion of the isolation region and the buried insulating layer thereunder to expose a part of the underlying substrate; forming a contact plug in the contact opening to electrically connect the underlying substrate, wherein the contact plug is surrounded by the isolation region and the buried insulating layer and physically in connection with the isolation region and the buried insulating layer, and has a top surface coplanar with that of the isolation region; and removing the mask layer to form a plurality of isolated silicon mesas after formation of the contact plug, wherein a top surface of the plurality of isolated silicon mesas is exposed and lower than that of the isolation region.