We report on the top-down fabrication of vertically-stacked polysilicon nanowire (NW) gate-all-around (GAA) field-effect-transistors (FET) by means of Inductively Coupled Plasma (ICP) etching and nanostencil lithography. The nanostencil is used to form sub-μm GAA gates over polysilicon NW array channels with high aspect ratio, considerably simplifying the lithographic steps above regions with deep 3D topography and non-planar surface features. This process lead to fabrication yields larger than 70% and authors envisage even larger yields of ⩾85% with optimized mask design. Electrical measurements confirm the results obtained from similar devices fabricated with a standard lithography method while achieving higher density, larger reproducibility and yield, maintaining the performance improvement related with scaling.