During the 1980's and 1990's the methods used to manufacture inertial MEMS devices could be divided into two groups; bulk and surface micromachining. Institutions which developed high precision inertial MEMS devices usually employed bulk micromachining processes. This was done to fabricate devices with large proof masses and stiff beams which result in a high scale factor, as well as high drive, and sense frequencies. New processes have been developed which are based on silicon on insulator (SOI) wafers. These processes combine the advantages of bulk and surface micromachining while enabling the etching of thick proof masses. This paper illustrates the manufacturing and performance advantages of an SOI inertial MEMS process.