An IDT electrode 2 and an electrode pad 3 are formed on one principal face of a piezoelectric substrate 1 and a circular electrode 4 is formed so as to surround these components. The circular electrode 4 is connected to a radiating conductor 15 formed on a bottom face of a circuit board 11 through a via conductor 14 formed within the circuit board 11. Thus, since heat generated in the IDT electrode 2 is easy to be released to the outside through the circular electrode 4, the via conductor 14 and the radiating conductor 15, adverse effects due to the heat can be prevented, thereby improving high power durability.