A semiconductor device has a heat dissipating base; a patterned insulating substrate attached to the heat dissipating base with a solder therebetween; a semiconductor chip attached to a conductive pattern of the patterned insulating substrate with a solder therebetween; a first conductor attached to the semiconductor chip with a solder therebetween; a resin case attached to the heat dissipating base with an adhesive; and a second conductor attached to the first conductor by laser welding. The second conductor formed by rolling has stripe-shaped rolling traces formed on a surface thereof in a rolling direction and is disposed on the first conductor such that the rolling traces are arranged in a same direction.