The agreement between the conception of minimal metal conductivity and experiment has been shown. It is found, that the smoothness of metal-insulator transition observed in crystal semiconductors is caused either by disorder and then we need the percolation theory to be used for data interpreting at T=0 K, or by small value of critical concentration of carriers. The critical concentration depends on the compensation level, classical and natural widening of defect level or correlated distribution of impurities. According to experimental data, the characteristic parameters of transition in n-CdSnAs₂, p-CdSnAs₂<Cu>and p-Ge has been obtained by the extrapolation to T=0 K.