A resin casing is insert-molded while clamp protrusions of clamp portions formed in bonding portions of lead terminals are put between an upper mold and a lower mold. An insulating substrate which has a wiring pattern mounted with semiconductor elements is fitted into an opening portion of the resin casing and adhesively bonded to the resin casing. Electric connection between the semiconductor elements and the bonding portions of the lead terminals and between the wiring pattern on the insulating substrate and the bonding portions of the lead terminals is made by bonding wires. Thus, it is possible to provide a method for manufacturing a semiconductor device and the semiconductor device, in which stress applied to lead terminals of a lead frame formed by insert molding can be suppressed, and wire bonding properties and reliability can be improved even when the thickness of each of the lead terminals is reduced.