A semiconductor module comprising: a substrate formed of a metal; an insulating layer formed on the substrate ; a plurality of wiring patterns formed on the insulating layer ; a bare-chip transistor mounted on one of the plurality of wiring patterns via a solder; and a copper connector formed of a copper plate and connecting an electrode formed on a top surface of the bare-chip transistor and another one of the plurality of wiring patterns via a solder, wherein the copper connector includes a flat portion , a first leg portion folded downward extending from one end of the flat portion and bonded to the electrode, and a second leg portion folded downward extending from the other end of the flat portion and bonded to the another one of the plurality of wiring patterns to form a bridge shape, and wherein the first leg portion comprises a width-reduced portion folded downward extending from the one end of the flat portion to have a taper shape gradually decreasing a width of the width-reduced portion from the one end of the flat portion , and a stress-reducing portion having a shape for reducing stress acting on the bonding face is formed on the bonding face of the first leg portion bonded to the electrode, wherein a notch portion is formed as the stress-reducing portion in the bonding face , or the bonding face is formed to have a small thickness, as the stress-reducing portion , or a chamfered portion is formed as the stress-reducing portion at a corner of the bonding face , or a hole is formed as the stress-reducing portion at the center of the bonding face , wherein notches are formed in the width-reduced portion on both sides in a width direction of the first leg portion , so as to face each other, and notches are formed on both sides in a width direction of the second leg portion , so as to face each other, each of the notches having a semi-circular shape, wherein the notches form a dumbbell portion having a dumbbell shape for reducing the stress acting on the bonding face in each of the first leg portion and the second leg portion . a substrate formed of a metal; an insulating layer formed on the substrate ; a plurality of wiring patterns formed on the insulating layer ; a bare-chip transistor mounted on one of the plurality of wiring patterns via a solder; and a copper connector formed of a copper plate and connecting an electrode formed on a top surface of the bare-chip transistor and another one of the plurality of wiring patterns via a solder, wherein the copper connector includes a flat portion , a first leg portion folded downward extending from one end of the flat portion and bonded to the electrode, and a second leg portion folded downward extending from the other end of the flat portion and bonded to the another one of the plurality of wiring patterns to form a bridge shape, and wherein the first leg portion comprises a width-reduced portion folded downward extending from the one end of the flat portion to have a taper shape gradually decreasing a width of the width-reduced portion from the one end of the flat portion , and a stress-reducing portion having a shape for reducing stress acting on the bonding face is formed on the bonding face of the first leg portion bonded to the electrode, <EOS>