Power electronics tends to go higher in frequency and higher in power density. This requires integrated transformers which are able to withstand high temperature (over 200˚C). This paper addresses the manufacturing and test of low power transformers used for the isolation in gate circuits power supplies. The transformers are built from a magnetic substrate (ferrite) using a microfabrication process detailed in the paper. The presented transformers are intended for power below 1 W, voltage circa 10 V, switching frequency of 1 MHz, temperature ranging from –55˚C to 200˚C and an isolation capacitance below 10 pF.