[en] Basing upon complex researches of monocrystals FZ-Si, a mechanism of microdefect formation is confirmed. It is established that the formation of microdefects happens by two mechanisms: vacancy and interstitial ones. The comparison of the data on CZ-Si and FZ-Si shows that this mechanism can be applied to CZ-Si with allowance for a modification of growth conditions and is significant for a larger content of impurities