A method of manufacturing a semiconductor device of the present disclosure includes the steps of sequentially forming an adhesion-improving film, a Pt film, a Sn film, and an Au film on a semiconductor wafer through vapor deposition; dicing the semiconductor wafer to obtain a semiconductor element; sequentially forming a Ni film and an Au film on a substrate through vapor deposition; and laminating the semiconductor element and the substrate so that the Au film formed on the semiconductor element and the Au film formed on the substrate face each other, followed by joining the semiconductor element and the substrate through heating.