How to stop erosion below my patio.?

I have a concrete slab patio. The yard slopes downhill at the base of he patio and the dirt under the patio is slowly washing away, beginning to expose the underside of the slab. What is the best way to stop this. The area in question is about 6 feet wide. I plan to place steps at this spot that go down to the rest of the yard, but want to stop the erosion first. Thanks!