Solid electrolytic capacitors are conventionally used for personal computers and so on.
Recently, an instant supply of current to a circuit has been required because of increase in frequency of CPUs for use in personal computers. Therefore, development of a solid electrolytic capacitor featuring a decreased equivalent series resistance in high frequency regions has been demanded.
As such solid electrolytic capacitors, solid electrolytic capacitors including an anode formed of a metal, such as tantalum and so on, a dielectric layer of an oxide of such a metal formed on the anode, and an electrolytic layer and a cathode deposited on the dielectric layer are generally used.
As the cathode of such solid electrolytic capacitors, two layers of a carbon layer and a silver layer deposited on the electrolytic layer are generally used.
However, the cathode of the two layers of the carbon layer and the silver layer has a problem as follows. Because a contact resistance between the carbon layer and the silver layer is increased due to differences in properties between the carbon layer and the silver layer, the equivalent series resistance in the high frequency regions is increased.
Therefore, for example, JP-A-10-242000 discloses a solid electrolytic capacitor including the cathode comprising three layers of a carbon layer, a mixed layer of carbon and silver and a silver layer formed on an electrolytic layer for the purpose of decreasing the equivalent series resistance in the high frequency regions.
However, according to results of examinations made by inventors of the present invention, in the case of forming the three layers of the carbon layer, the mixed layer of carbon and silver, and the silver layer as the cathode on the electrolytic layer as mentioned above, the contact resistance between the mixed layer of carbon and silver and the silver layer was increased and it was still impossible to sufficiently decrease the equivalent series resistance in the high frequency regions.