In the process of forming the heat-generating layer 80, the extraction electrodes 85 a, 85 b shown in FIG. 4 maybe formed by sputtering, for example. [0054] Thereafter, on the upper shield layer 38 and heat-generating layer 80, an insulating layer 39 made of an insulating material such as Al2O3 is formed with a thickness of about 0.1 ??m to about 0.5 ??m by sputtering, for example.