1. A method for executing multiple tasks in a mobile device, the method comprising: detecting, by the mobile device, a first execution event for executing a first application; identifying a type of the first execution event; executing the first application in one of a full mode and a mini mode according to the type of the first execution event; displaying an execution screen of the first application executed in the one of the full mode and the mini mode; after the displaying of the execution screen of the first application executed in the one of the full mode and the mini mode, subsequently detecting a second execution event for executing a second application represented by one of items included in a displayed tray, each of the items representing an application to be executed in one of the full mode and the mini mode; executing the second application in another of the full mode and the mini mode in response to the detected second execution event; and displaying an execution screen of the second application executed in the other of the full mode and the mini mode along with the displayed execution screen of the first application executed in the one of the full mode and the mini mode.