An rf remote plasma oxidation technique to form an insulating barrier was carried out to enhance properties of CoFe/AlOx/CoFe magnetic tunneling junctions. The rf remote plasma method was found to reduce self-bias effect on the barrier during the rf oxidation process and to increase atomic oxygen concentration in a plasma state. Experimentally observed rms roughness of the barrier in our magnetic tunnel junction was decreased from 5 to 1.5 Angstrom. In addition, electrical breakdown voltage and magnetoresistance of our magnetic tunnel junction devices were increased from 0.8 V up to 1.2 V and from 7% up to 30%, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.