The new five-and-a-half year deal will keep the 26-year-old defender at Stamford Bridge until the summer of 2016.
“It is good news for me, it is a very big step for me in my career and I want to give my maximum and try to help Chelsea win a lot more trophies,” he told the club’s official website.
“These things take a little time but my first vision was always to stay with Chelsea, there were not a lot of problems because I wanted to stay, the club wanted me to stay and I want to thank everyone who helped with the deal, I am very happy with that.
“I don’t like to think too much about the past because in football you have to get better every day, concentrate on small details of every game, but from my side maybe the two goals against Liverpool gave me confidence, but all other things have been slowly developing and step-by-step, which is what I have to do in the future.
“For every player coming to a new country you have to adapt and then you become better and better, but I now feel so comfortable here and I really enjoy being a Chelsea player and my wish was always to stay here.
“Now I think I can give many more good games, the three years has gone very quickly, and I think it has been a success so I hope to carry on getting better and better with Chelsea.”