Methods of making a current-perpendicular-to-the-planes (CPP) type sensor by ion milling to the spacer layer using a mask without undercuts

A method of making a current-perpendicular-to-the-planes (CPP) type sensor, the method comprising the acts of:

• depositing a plurality of sensor layers over a first electrically conductive lead layer of the sensor;
• forming, over the sensor layers, a mask without undercuts in a central region;
• with the mask without undercuts in place:
• starting an ion milling process to remove sensor layer materials, including spacer layer materials, left exposed by the mask without undercuts in end regions which surround the central region;
• stopping the ion milling process at or near the removal of the spacer layer materials in the end regions, to thereby refrain from removing most if not all of an electrically conductive layer formed beneath the spacer layer, for forming a read sensor structure having a free layer with sidewalls that are in alignment with sidewalls of a spacer layer;
• depositing insulator materials in the end regions and over the aligned sidewalls of the free layer and the spacer layer;
• removing the mask without undercuts through use of a planarization process;
• and
• forming a second electrically conductive lead layer of the sensor over the read sensor structure.