A new processing technique to realize an extremely long cantilever structure having a length of a few mm using a silicon-on-insulator(SOI) wafer has been developed. By adding only one Si selective wet etching process after the usual HF sacrificial layer etching, the detachment length of a cantilever became at least 10 times longer than that formed using conventional method. This technique is easily applicable to the fabrication of various SOI-MEMS without the use of any special apparatus.