A semiconductor device is provided which has a capacitor insulating film made up of zirconium aliminate being an amorphous film obtained by having crystalline dielectric contain amorphous aluminum oxide and having its composition of Al.sub.XZr.sub.(1-X)O.sub.Y (0.05.ltoreq.x.ltoreq.0.3), hereby being capable of preventing, in a process of forming a capacitor of MIM (Metal Insulator Metal) structure, dielectric breakdown of a capacitor insulating film while a relative dielectric constant of a metal oxide film used as the capacitor insulating film is kept high.