Membrane structure and a manufacturing method thereof

A membrane structure (carbon insulating membrane structure) which comprises carbon and an insulating film, said insulating film being formed of fluorinated magnesium oxide, provided on the carbon. The amount of fluorine added to the magnesium oxide is 0.0049-0.1508 atom% inclusive. This membrane structure contributes to the realization of electronic devices using carbon typified by graphene, for example, spin devices. This membrane structure is formed by, for example, sputtering using a target which contains magnesium oxide and magnesium fluoride.