Lead frame making method, semiconductor device making method and semiconductor device

A method of manufacturing a lead frame, a semiconductor device and a method of manufacturing a semiconductor device, which is a lead frame for a semiconductor device lead frame having the semiconductor chip is electrically connected in the sealing resin, and at least a portion of the seal from the following the following manner is exposed resin sealing the lead portion in said sealing resin. The above-described methods, comprising: the step of forming the lead portion and punching step from the top side of the lead portion after the punching step by flattening processing direction from below toward the upper side to side punching.