Provided are an electron multiplier electrode using a secondary electron extraction electrode and a terahertz radiation source using the electron multiplier electrode. The ROM cell array is coupled to a plurality rows of bit-lines and a plurality columns of word-lines and comprises: a plurality of sub-cell-arrays arranged along the column direction, each sub-cell-array comprising a plurality of unit cell structures. In addition, each USB module maybe used as a stand alone unit by snapping a sleeve onto the rear of the module.