Sembie-Ferris accepts contract.
The young winger has burst onto the first team scene in the past few months and has been rewarded with a new three year deal.
After making his U's debut at Cardiff City in an FA Cup Third Round tie in January, the eighteen year old made ten league appearances in the second half of the season.
The last three were eye catching cameo roles in the finale to the season, helping the U's gain seven points from nine towards League One survival on the final day.
And Dion was delighted to sign an extended deal, keeping him contracted until the summer of 2018.
"It was great to be offered a new contract and I'm really pleased that all my hard work has been recognised by the manager and the club.
"Colchester United is a fantastic place for any young player to be playing football and I'm very grateful to have been given the opportunity to stay another three years.
"It's all signed now so I can enjoy my summer break and come back for pre-season ready to push on and play as much first team football as I can."