An apparatus and method for improving the underfill filling of a semiconductor chip element 100 which is ultrasonically bonded to and mounted on a circuit board. A semiconductor chip element 100 includes a silicon chip 101 and a group of stud bumps 117 formed on a bottom surface 101a of the chip 101. Signal stud bumps 113 are made of gold while power stud bumps 114, ground stud bumps 115 and dummy stud bumps 116 are all made of a gold-palladium alloy, which are harder than the signal stud bumps 113 and thus do not deform easily during ultrasonic treatment. Therefore, in a state in which the semiconductor chip element 100 is mounted, a gap of approximately 30 &mgr;m is maintained between the bottom surface 101a of the chip 100 and a top surface of the circuit board 120 on which the semiconductor chip element 100 is mounted.