Techniques in fabricating a fin field-effect transistor (FinFET) include providing a substrate having a fin structure and forming an isolation region having a top surface with a first surface profile. A dopant species is implanted using a tilt angle to edge portions of the top surface. The edge portions are then removed using an etch process. In this respect, the isolation region is modified to have a second surface profile based on an etching rate that is greater than an etching rate used at other portions of the top surface. The second surface profile has a step height that is smaller than a step height corresponding to the first surface profile. The tilt implantation and etching process can be performed before a gate structure is formed, after the gate structure is formed but before the fin structure is recessed, or after the fin structure is recessed.