A lead frame for a semiconductor IC device has a pair of common elongated leads and first and second groups of slender leads arranged on opposite sides of the common elongated leads and generally extending transverse to the common elongated leads. The common elongated leads have as their integral parts slender leads extending therefrom generally transverse thereto and substantially linear extensions from both ends of the common elongated leads. The linear extensions serve to firmly support a semiconductor chip to be packaged along with parts of the leads. The common elongated leads may further have as their integral parts projections extending from their sides for enhancement of the heat dissipation capability. A semiconductor chip may have bonding pads arranged thereon such that bonding wires and the common elongated leads do not cross each other for electrical connection between the common elongated leads and bonding pads of the semiconductor chip.