Two types of miniature resistance thermometers based on Ge films on a semi-insulating GaAs substrate have been developed and fabricated. They can operate in the temperature range from 0.5 to 300 K. The properties of these thermometers at low temperatures and in magnetic fields up to 14 T have been studied. The temperature dependencies of resistance and magnetoresistance of the thermometers, as well as the temperature measurement errors induced magnetic fields, are presented.