A method for manufacturing a semiconductor device includes: preparing a first substrate; forming a metal film having a Ti layer as the most outermost surface on one surface of the first substrate a metal film having a Ti layer as the outermost surface; patterning the metal film to form a first pad portion; preparing a second substrate; forming on one surface of the second substrate a metal film having a Ti layer as the outermost surface; patterning the metal film to form a second pad portion; vacuum annealing the first substrate and the second substrate to remove an oxide film formed on the Ti layer in the first pad portion and the second pad portion; and bonding the first pad portion and the second pad portion together.