A semiconductor device includes a first substrate, an aluminum pad, a first nickel electrode, a second substrate, a second nickel electrode, and a connection layer. The first substrate includes a wiring therein. The aluminum pad is provided adjacent to a surface layer of the first substrate and is connected to the wiring. A portion of the first nickel electrode extends inwardly of the first substrate and is connected to the aluminum pad. A top surface of the first nickel electrode projects from a surface of the first substrate. A portion of the second nickel electrode extends inwardly of the second substrate. A top surface of the second nickel electrode projects from a surface of the second substrate facing the first substrate. The connection layer comprises an alloy including tin and connects the first nickel electrode and the second nickel electrode.