PURPOSE: To rapidly activate an impurity at a low temperature by introducing the impurity and then so irradiating a semiconductor single crystalline layer with an X-ray as to satisfy Bragg's conditions.

CONSTITUTION: A doped layer 2 is formed by ion implanting on a P-type Si substrate 1(100) under the conditions of 80keV of 31P+ and 5×1015cm-2. The Si surface (100) is so irradiated with an X-ray 3 having 1.54060 of wavelength and 100μW/cm2 from the crystal orientation (100) of the substrate 1, i.e., a direction of 55.434 degrees by a substrate normal line as to satisfy Bragg's reflecting conditions. Since the layer 2 can be substantially completely activated by this operation, a high concentration impurity active layer 4 can be formed particularly without heating. The type and introducing method of the impurity is not limited. Even if it is radiated with the X-ray at the time of introducing the impurity, similar effects can be obtained.