A semiconductor package includes a uniform thin insulating film covering the internal circuit formed on a silicon substrate. A plurality of thick island insulating films are formed underlying respective pad electrodes, which connect the internal circuit to an external circuit. The silicon substrate is polished from the bottom to have a thickness less than 0.6 mm. The thick island insulating films reduces an electrostatic capacitance of the pad electrodes to reduce the propagation delay of a signal passing through the pad electrodes.