PURPOSE: To avoid a thermal stress caused by the variation of a treatment temperature and nonuniformity of heating by a method wherein a semiconductor substrate is tightly brought into contact with a holder having an excellent and uniform heat conducting property to heat the substrate surface uniformly.

CONSTITUTION: A Schottky electrode 2 and an ohmic electrode 3 are formed on the surface and the rear of a semiconductor substrate 1. A substrate holder 4 made of Al has a lager area than the substrate 1. The ohmic electrode 3 forming surface of the substrate 1 is tightly brought into contact with the holder 4 and held by protrusions 5. The holder 4 on which the semiconductor substrate 1 is mounted is fitted to the trench of a quartz board 6 and inserted into a quartz tube 8 whose inside temperature is 400°C to subject the ohmic electrode 3 to a thermal treatment for alloying. The substrate 1 is heated uniformly through the holder 4, so that a thermal stress which breaks the Schottky electrode 2 can be suppressed and the ohmic electrode can be subjected to a thermal treatment without causing the deterioration of a breakdown strength. If a substrate holder is produced by evaporating Au on an Si substrate having an excellent heat conducting property, a thermal conductivity can be further improved.