A filter for trapping, sterilizing, and decomposing organic matter,
bacteria, viruses, and other harmful substances is provided at low cost
and extremely high efficiency. A semiconductor material having a light
emitting function is formed in the interior or on the surface of a porous
ceramic material substrate by deposition from a suspension of
semiconductor particles, and an electrode provided to serve as a filter.
Voltage is applied so that ultraviolet light is emitted while a fluid is
being filtered, and any harmful substances are filtered and
simultaneously sterilized and decomposed.