A lead frame adapted to a semiconductor package, which is enclosed in a molded resin body and is connected with a board, is formed by processing a thin metal plate so as to include a stage for mounting a semiconductor chip thereon, a plurality of leads arranged to encompass the stage, and a plurality of lead interconnecting members (or dam bars) for interconnecting the leads together. At least one recess, which is of a circular shape or a non-circular shape, is formed on the backside of the lead (or the lead interconnecting member), which is substantially arranged in the same plane with a terminal surface of the molded resin body. Due to the formation of the recess that is subjected to plating, it is possible to increase the joining strength between the lead and solder; hence, it is possible to improve reliability regarding electric connection between the semiconductor package and board.