shape when viewed from the top as shown in fig6 after the formation of the via hole 24 a in the insulating layer 24 a magnetic material layer 26 is conformally deposited on the insulating layer 24 and on the interior surface of the via hole 24 a by physical vapor deposition pvd or atomic layer deposition ald methods the magnetic material layer 26 is a thin film with uniform thickness and the magnetic material layer 26 does not fill up the via hole 24 a according to the embodiment the magnetic material layer 26 has a thickness that is greater than that of the magnetic material layer 20 according to the embodiment the magnetic material layer 26 may be composed of a material including but not limited to nife nifeco cofe cofeb fe co ni alloys or compounds thereof and or other magnetic materials as shown in fig7 an anisotropic dry etching process is carried out to etch the magnetic material layer 26 thereby forming an annular sidewall spacer 26 a extending vertically along the sidewall of the via hole 24 a the magnetic material layer 26 outside the via hole 24 a is removed to reveal the top surface of the insulating layer 24 after the etching back of the magnetic material layer 26 an insulating layer 27 such as silicon oxide is deposited over the substrate 100 the insulating layer 27 fills up the remaining.