The inventive fabrication process for magnetoresistive devices (CPP-GMR devices) involves the formation of a zinc oxide or ZnO layer that provides the intermediate layer of a spacer layer, comprising Zn film formation operation for forming a zinc or Zn layer and Zn film oxidization operation for oxidizing the zinc film after the Zn film formation operation. The Zn film formation operation is implemented such that after a multilayer substrate having a multilayer structure before the formation of the Zn film is cooled down to the temperature range of −140° C. to −60° C., the formation of the Zn film is set off, and the Zn film oxidization operation is implemented such that after the completion of the Zn film oxidization operation, oxidization treatment is set off at the substrate temperature range of −120° C. to −40° C. Thus, excelling in both flatness and crystallizability, the ZnO layer makes sure the device has high MR ratios, and can further have an area resistivity AR best suited for the device.