Method of making fault-free surface zone in semiconductor devices by step-wise heat treating

In a gettering method for processing semiconductor wafers a semiconductor wafer such as a silicon wafer is first annealed in a non-oxidizing atmosphere, for example, in a nitrogen atmosphere, at a temperature in the range of 950° to 1,300° C., preferably at 1,050° C., for more than 10 minutes, for example for four (4) hours, to diffuse out oxygen near the surfaces of the semiconductor wafer. Then the semiconductor wafer is annealed at a temperature in the range of 600° to 800° C., for example at 650° C., for more than one hour, preferably for 16 hours, to create in the interior of the semiconductor wafer microdefects of high density.