The present invention relates to a method for fabricating a planar independent-double-gate FET or a planar gate-all-around FET on a bulk semiconductor substrate. The method comprises refilling a surface recess in an active semiconductor region with a buried sacrificial layer, and, after preparing a pre-processing a gate stack by respective deposition and patterning, the formation of a recess in the isolation regions so as to cause the recess to extend, in a depth direction that points towards the inner substrate, to a depth level that allows removing the buried sacrificial layer and so as to cause the recess to undercut portions of gate stack in the channel direction.