Azarenka assumed control from the first game, breaking Stephens's serve after clawing her way back from 40-15 down before comfortably holding her own.
The teenager was struggling to make an impact on the defending champion's serve, while she found herself continually fighting against the riptide.
The Belarusian broke twice more as she went on to clinch the opening set.
Her dominance continued early in the second set as she once again went 1-0 ahead, but thereafter Stephens's forehand began to find the mark.
She managed to get the break back in the next game and then consolidated.
For the second time in two matches, it looked like the American might profit from an injury to her opponent, as Azarenka seemed to be struggling with an ankle problem.
Stephens looked as if she might be gaining the upper hand, but soon Azarenka was back on top, breaking for a 4-2 lead.
Again the 19-year-old responded in the next game and Azarenka showed her frustration by smashing the ball hard into the plexicushion when returning to her seat at the changeover.
However, a third break in as many games meant that Azarenka had the chance to serve for a place in the final.
After more than 12 minutes and five match points, Azarenka relinquished her serve once more. It was confirmed by a spectacular forehand down the line from Stephens.
When the 23-year-old returned to the court, she was able to break for a seventh time to eventually seal her passage into the final.