NOVELTY - A hardenable silicone composition contains polyorganosiloxane (A) having 2 or more alkenyl groups in a molecule, polyorgano hydrogen siloxane (B) and hydrosilylation catalyst and/or radical initiator (C). The component (B) is reaction product of organosiloxane oligomer having 2 or more hydrogen atoms bonded with silicon atom, and isocyanurate compound having alkenyl group(s) in a molecule. The component (B) is compounded in an amount of 0.01-3.0 mol of hydrogen atoms bonded with silicon atom with respect to 1 mol of alkenyl groups in component (A).    USE - Hardenable silicone composition used for adhering and/or sealing semiconductor element such as phototransistor, photodiode, solar cell module, in semiconductor device (claimed).    ADVANTAGE - The composition improves the adhesiveness with respect to metal electrode and enables to manufacture highly reliable semiconductor device.    DETAILED DESCRIPTION - A hardenable silicone composition contains polyorganosiloxane (A) having 2 or more alkenyl groups in a molecule, polyorgano hydrogen siloxane (B) and hydrosilylation catalyst and/or radical initiator (C). The component (B) is reaction product of organosiloxane oligomer having 2 or more hydrogen atoms bonded with silicon atom, and isocyanurate compound having alkenyl group(s) in a molecule. The component (B) is compounded in an amount of 0.01-3.0 mol of hydrogen atoms bonded with silicon atom with respect to 1 mol of alkenyl groups in component (A). The component (B) is used as in an amount of 0.01-1.5 mol of the reaction product of organosiloxane and isocyanurate. An INDEPENDENT CLAIM is included for semiconductor device (1), which consists of semiconductor element (2) sealed and/or adhered using the cured material (4) of the hardenable silicone composition.    DESCRIPTION OF DRAWING(S) - The drawing shows the sectional view of a semiconductor device.    Semiconductor device (1)    Semiconductor element (2)    Substrate (3)    Cured material (4)    Lead electrode (5)