Ant Problems not going away?

For awhile now we have been having problems with ants inside the home. there is not an ant trail, they are tered all over the house like some in the bathrooms, kitchen, and some come out from under the carpet trim. I have put Ortho powder on the ant mounds outside the house and for awhile there the ants disapear but come back after awhile. What is the best solution for this? Is there a posibilty that the ants have built a mound under the carpet?