This invention relates to a compound of formula I:or a pharmaceutically acceptable salt thereof. The semiconductor device includes: a substrate provided with a trench formed in the substrate; and at least one device isolation structure including an oxide layer formed on the trench, a nitride layer formed on the oxide layer disposed on sidewalls of the trench and a high density plasma oxide layer formed on the nitride layer to fill the trench. An event queue system is coupled to the protocol terminator system to store the events in an event queue.