The sophomore guard had a spectacular season which culminated with him winning the Pac-12 Player of the Year Award.
The Tar Heels (29-6) never trailed and moved on to face fifth-seeded Auburn on Friday in a Midwest Regional semifinal.
Noah Dickerson had 20 points and 12 rebounds, and ninth-seeded Washington made a successful return to the NCAA Tournament for the first time in eight years, beating Utah State 78-61 on Friday.
Washington had a long scoring drought in the second half, shot 33 percent and went 5 for 23 from the 3-point arc.
After struggling in the first half, Washington (26-7) kicked its long-armed, swarming defense into a faster gear and the fifth-seeded Buffaloes (21-12) had trouble handling it.