Provided are a lead frame and a semiconductor package which allows reliable attachment of a small-sized semiconductor chip requiring a large number of leads to a board while providing high heat dissipation capability. The semiconductor package includes leads, each having a top plate extending inward from the outside edge of a frame and a plurality of pillar-shaped portions supporting the top plates, a semiconductor chip attached onto edge portions of the leads, wires connecting the leads with corresponding bonding pad on the semiconductor chip, and a molding material encapsulating the semiconductor chip and the wires and parts of the leads so as to the bottom surfaces of the leads are exposed. Further, some embodiments have a conductive pad exhibiting higher heat dissipation.