first hard mask with a second hard mask e g polysilicon with good selectivity to oxide may be particularly advantageous in semiconductor devices such as a 3d memory device one exemplary advantage of replacing the first hard mask having a high tensile strength with a second hard mask with good selectivity to oxide is that bending stringers and residues that can cause bridging leakage in the high aspect ratio structures during the bit line formation can be reduced or eliminated another exemplary advantage of replacing the first hard mask having a high tensile strength with a second hard mask with a good selectivity to oxide is that the thickness of the hard mask can be reduced lowering the aspect ratio and making the world line formation easier another exemplary advantage of replacing the first hard mask having a high tensile strength with a second hard mask with a good selectivity to oxide is that a damascene gate process can be used to reduce or eliminate stringers and residues that cause bridging leakage in the case of the first hard mask being silicon nitride the thickness of silicon nitride that would be needed to perform the damascene gate process due to its poor selectivity to oxide would significantly increase the thickness and aspect ratio of the device replacing the silicon nitride with a second hard mask that has good selectivity to oxide such as polysilicon allows for the gate damascene process to be used and the associated advantages e g reduction or elimination of stringers and residues that cause bridging leakage to be realized.