Tunnel magnetoresistance (TMR) devices were processed by sputter deposition of Co, Al and NiFe on oxidized Si wafers. After the Al deposition, an ex-situ oxidation in air at room temperature or an in-situ oxidation enhanced by ultraviolet (UV) irradiation in high purity oxygen at 100 mbar follows. The electrical and magnetic properties of the junctions are measured and discussed concerning specific junction resistance, magnetoresistance ratio, long time stability of the junctions, and failure rate of the processes. Some microscopic experiments provided consistent information of the tunnel barrier. MR ratios between 15% and 20% were measured for the different oxidation processes
