by exploiting an intense correlation exhibited between the distribution of lattice distortions in a wafer and the distribution of the threshold voltages of field effect transistors , the distribution of the lattice distortions in the wafer is reduced , thereby to mitigate the distribution of the characteristics of the semiconductor elements inthe wafer . the difference between the maximum value and minimum value of the lattice distortions of a gaas single crystal at a normal temperature is set to at most 4 × 10 - 5 , and the density of si atoms contained in the gaas single crystal is set to at most 1 × 10 16 cm - 3 , whereby the characteristics of semiconductor elements whose parent matrial is the gaas single crystal can be made uniform .