A semiconductor device comprises a plurality of leads respectively made up of an inner lead and an outer lead, a semiconductor chip electrically connected to the inner leads of the leads, and a package encapsulating at least the inner leads of the leads and the semiconductor chip so that the outer leads extend outwardly of the package. The package has an upper part and a lower part which have mutually different sizes such that a stepped part is formed between the upper and lower parts by the different sizes, and each of the outer leads have a wide part which is wider than other parts of the outer lead extending outwardly of the package only within the stepped part of the package.