A method for forming a bi-layer lift-off mask for use in fabricating an abutted junction type GMR read-head sensor with a narrow trackwidth of less than 0.5 microns. The mask has a novel suspension bridge structure that avoids problems associated with bilayer lift-off masks of the prior art, namely insufficient or excessive undercutting of the lower layer that produces fence formations in the conducting lead layer or collapse of the mask structure rendering removal difficult.