the features of these layers the arrangement and composition of the above described layers have a number of advantages first the sputtered ta 2 o 5 layer 20 and its position within the structure provides the final dielectric layer 20 39 with relatively low leakage current on the microscopic level much lower than can be achieved from anodizing an elemental tantalum layer however sputtered ta 2 o 5 layers have a relatively high number of pin hole defects on the order of 2 to 5 per square centimeter when a sputtered ta 2 o 5 layer is used alone as the dielectric layer the pin hole defects in the sputtered layer create large and unacceptable leakage currents making sputtered ta 2 o 5 layers useless for capacitors greater than 0 25 square centimeter the inventors characterize this by stating that sputtered ta 2 o 5 layers have low 34 microscopic 34 leakage current very low in any one small area but large 34 macroscopic 34 leakage currents very large in any large area in contrast the anodization of tantalum layer 18 has been found to create a dielectric layer with much fewer pin hole defects leading to a low macroscopic leakage current but with a larger microscopic leakage current it is believed that elemental tantalum migrates through the dielectric layer during the anodization process as the dielectric layer is being created thereby creating conductive paths through the dielectric layer on a microscopic level however since the sputtered ta 2 o 5 layer 20 is in series with the anodized product of tantalum layer 18 the overall dielectric layer 20 39 obtains the benefits of both sub layers low microscopic leakage current being provided by layer 20 and low pin hole.