Stephenson struck after 118 minutes of a contest that saw Boro rewarded for a battling performance that kept Derby at bay.

Goalkeeper Sol Brynn made a number of outstanding saves and central defender Nicholas Hood made one terrific block to deny the visitors as Boro stuck to the task doggedly.

With the game deep into extra time, Stephenson tested Derby’s Sam French for the first time when he was released through on goal, but the visiting goalkeeper proved equal to the task.

Moments later, Stephenson was handed a similar opportunity, and this time he made no mistake in rifling the ball beyond French and into the Derby goal to spark wild celebrations.

Boro will now face Manchester City in the final of the competition on Saturday March 9 at a venue to be confirmed.

Boro: Brynn, Dodds, Hood, Wood, Robinson, Sykes, Balde (Ridley 74), Spence, McGill (Coburn 85), Hackney, Wearne (Stephenson 51).