There is provided a crystal oscillator in which a crystal blank and an integrated circuit (IC) chip are accommodated in a vessel and the IC chip is fixed through a bump to the bottom surface of the vessel by means of ultrasonic thermocompression bonding. The IC chip contains an oscillation circuit utilizing the crystal blank and has a plurality of terminal electrodes on a major surface thereof. A plurality of connection terminal portions are formed on the bottom surface of the concave portion of the vessel so that each of the connection terminal portions corresponds to one of the terminal electrodes. Each of the connection terminal portions is formed into a rectangular shape and the width of each connection terminal portion is identical. The terminal electrodes and the connection terminal portions are bonded to each other through a bump by means of ultrasonic thermocompression bonding. Thus, the IC chip is fixed to the bottom surface of the concave portion of the vessel.