An exemplary structure for the fin field effect transistor comprises a substrate comprising a major surface; a plurality of fin structures protruding from the major surface of the substrate, wherein each fin structure comprises an upper portion and a lower portion separated at a transition location at where the sidewall of the fin structure is at an angle of 85 degrees to the major surface of the substrate, wherein the upper portion has sidewalls that are substantially perpendicular to the major surface of the substrate and a top surface having a first width, wherein the lower portion has tapered sidewalls on opposite sides of the upper portion and a base having a second width larger than the first width; and a plurality of isolation structures between the fin structures, wherein each isolation structure extends from the major surface of the substrate to a point above the transition location.