Method of processing a substrate containing at least one semiconductor of the Si.sub.XA.sub.Y type and comprising at least four separate types of light elements, comprising at least the following steps: carrying out a first anneal of the substrate at a temperature T1 corresponding to a thermal activation temperature for a first one of the four types of light elements, carrying out a second anneal of the substrate at a temperature T2 corresponding to a thermal activation temperature for a second one of the four types of light elements, carrying out a third anneal of the substrate at a temperature T3 corresponding to a thermal activation temperature for a third one of the four types of light elements, carrying out a fourth anneal of the substrate at a temperature T4 corresponding to a thermal activation temperature for a fourth one of the four types of light elements, each anneal comprising a holding at the temperature T1, T2, T3 or T4 and the temperatures T1, T2, T3 and T4 being such that T1>T2>T3>T4.