PURPOSE: To miniaturize a crystal oscillator which is used as a reference signal generation source.

CONSTITUTION: An IC 4 is mounted in advance in a center part of a substrate 1 on which a wiring pattern 2 is provided on the upper face. On a specific connecting pad in plural connecting pads 5 provided on the upper face of the IC 4, a crystal resonator 7 of a tuning fork type is fixed so as to hold a parallel state to the IC 4 through a stud bump 8. The crystal resonator 7 and the stud bump 8 are subjected to flip chip bonding. Each remaining other connecting pad 5 and a wiring pattern 2 are connected by a bonding wire 6. By fixing a sealing cap to the outside periphery of the wiring pattern 2, the whole circuit element including the IC 4 and the crystal resonator 7 is sealed, and a crystal oscillator is formed. Since the crystal resonator 7 is fixed in advance so as to hold a parallel state to the IC 4 on the upper face of the IC 4, an area of the substrate can be made small, and also, since the crystal resonator is connected to the IC through the stud bump, a characteristic of the crystal oscillator is improved.