Patent ID: 7508631

Claim:
A magnetic disk device having: a magnetic disk arranged rotatably; a magnetic head slider arranged in a manner of facing a surface of the magnetic disk; and a driving unit configured to move the magnetic head slider in a radial direction of the surface of the magnetic disk, wherein recording/reproduction is performed in a condition that an air stream is generated between the magnetic disk that is rotating and the magnetic head slider, to cause the magnetic head slider to fly, wherein the magnetic head slider has a silicon slider-substrate-portion and a thin-film head portion which is formed directly on the slider substrate portion using a thin-film process and forms an air-bearing surface along with the slider substrate portion, and wherein the thin-film head portion has a recording/reproduction element facing the surface of the magnetic disk and a ceramic insulation film which has alumina and silicon-based ceramics in order to have the approximately same coefficient of linear expansion as a coefficient of linear expansion of the silicon-slider-substrate portion wherein the silicon-based ceramics of the ceramic insulation film are formed in the in-plane direction behind the recording/reproduction element wherein the alumina ceramic completely encapsulates the silicon-based ceramic.