A vapor management system includes a fuel tank, a canister, a pressure control valve between the tank and canister and defining a high pressure side and a low pressure side, a vacuum source, a purge valve between the canister and vacuum source, a leak detection valve connected with the canister and including a processor. In addition, the lower surface of the second memory gate electrode is located lower in level than the lower surface of the first memory gate electrode. A displacement amount of the first piston and a displacement amount of the second piston are different. The first and second engagement members are movable between an engagement position and a withdrawal position with respect to the step portions.