Williams, a senior, was just 5 of 13 from the field but made two 3 pointers and added four steals. Malcolm Armstead had 17 points to lead the Shockers (5-0), who will face Iowa in Wednesday's Riviera Division final.
Brandon Young led the Blue Demons (2-2) with 19 points and five assists, and Moses Morgan added 15 points off the bench. DePaul shot just 31 percent from the field.
Wichita State wasn't much better, hitting 43 percent of its shots and 56 percent of its free throws. But the Shockers never trailed, leading by as many as 13 in the second half. The game was the first meeting between the schools since 1988.