Abstract: A single crystal silicon wafer is sliced off so as to have a slant surface that is inclined from plane (001) such that the normal of the slant surface is inclined by 0.01.degree. to 0.2.degree. from direction [001] toward direction [110]. After being cleaned, the silicon wafer is heat-treated at 600-1,300.degree. C. for not less than 1 minute in an ultrapure argon or hydrogen atmosphere containing nitrogen at not more than 0.1 ppm, to thereby cause the slant surface to have a stepped crystal surface structure. The stepped crystal surface structure is constituted of step walls Sa and Sb when it has been formed by a heat treatment in an argon atmosphere, and substantially all of its step walls are of a type Sb when it has been formed by a heat treatment in a hydrogen atmosphere.

Abstract: A semiconductor specimen is held by a stage which is equipped with a heater (and a cooler) to change the temperature of the specimen in a predetermined range. Minority carriers are generated in the specimen by irradiating it with an energy beam such as a laser beam. A signal reflecting the recombination process of minority carriers is detected in a non-contact manner by a combination of microwave oscillator and a microwave detector through the microwave impedance coupling with the specimen. Decay curves are obtained at a plurality of temperatures in the predetermined range. A deep impurity level in the specimen is determined by performing an Arrhenius' plot on the basis of the plurality of signal decay curves and the corresponding specimen temperatures.