Abstract: Disclosed herein is a deflash technique for removing flash from a portion of a semiconductor package to be plated before a plating process and after a sealing process accompanied by resin molding during the manufacture of semiconductors, and more particularly a semiconductor package having grooves formed at side flash, a groove forming method, and a deflshing method using the semiconductor package, for removing the side flash formed at a side portion of a lead frame where it is difficult to perform a deflashing process. Conventionally, it is impossible to completely remove side flash remaining on the lead frame at a region where it is difficult to perform a deflashing process even by injecting water jet or media at a very high pressure, or by irradiating laser beams thereto while changing irradiation directions.