High performance MIS field effect transistors on semi-insulating indium phosphide have been fabricated. The contacts and the channel are doped with silicon implantation. The passivation of the channel surface region is achieved by the growth of a 150 A thick specific anodic oxide, In(P03)3 condensed phosphate. The physico-chemical properties of this oxide, reported in details in a separate contribution to this conference, make this material an excellent candidate for the passivation of InP. The gate dielectric is completed with electron beam evaporated Al203. Depletion mode devices with a 2 micron channel length exhibit reproducible low saturation current drift (less than 4% after 1 hour) and high transconductance (100 mS/mm). They are well suited for integrated opto-electronics.