Floating zone, neutron transmutation-doped and magnetic Czochralski silicon crystals are being widely used for
fabrication power devices. To improve the quality of these devices and to decrease their production cost, it is necessary to
use large-diameter wafers with high and uniform resistivity. Recent developments in the crystal growth technology of
Czochralski silicon have enable to produce Czochralski silicon wafers with sufficient resistivity and with well-controlled,
suitable concentration of oxygen. In addition, using Czochralski silicon for substrate materials may offer economical
benefits. First, Czochralski silicon wafers might be cheaper than standard floating zone silicon wafers. Second, Czochralski
wafers are available up to diameter of 300 mm. Thus, very large area devices could be manufactured, which would entail
significant saving in the costs. In this work, the conventional Czochralski silicon crystals were grown with higher oxygen
concentrations using high pure polysilicon crystals. The silicon wafers were annealed by several steps in order to obtain
saturated oxygen precipitation. In those wafers high resistivity over 5,000 Ω·cm is kept even after thermal donor formation
annealing.