A method includes forming an anti-punch-through layer over a first region and a second region of a substrate, forming a semiconductor layer over the anti-punch-through layer, patterning the semiconductor layer and the anti-punch-through layer to form a first plurality of fins over the first region and a second plurality of fins over the second region, and forming a patterned resist layer over the first plurality of fins and the second plurality of fins. The method also includes recessing a portion of the substrate between the first plurality of fins and the second plurality of fins in an etching process through openings of the patterned resist layer.