Republic of Ireland U21 Shane Duffy has signed a contract extension at Everton that will keep him at Goodison Park until 2015.The defender has made four premier league appearances for the Merseysiders since joining as a scholar in 2008 and enjoyed loan spells at Burnley and Scunthorpe.The Derryman told evertonfc.com, “I’m delighted to get it done. It’s taken a bit of time but I am happy now.“I have been here for a while now and loved every minute of it. Now this is sorted I can focus on working hard and continuing to improve.”Duffy has been called up to Giovanni Trapattoni’s squads on several occasions but is yet to receive his first senior cap.