deposition and etching steps described above can be repeated n times n u2267 2 with each iteration comprising a deposition on at least one portion of the substrate 10 of a layer of predetermined thickness of a predetermined material followed by an anisotropic etching of the same layer with the realization of at least a relative spacer analogous to the spacer seed 22 perpendicular to the upper surface 12 of the substrate 10 more in particular as better highlighted in fig6 the method thus provides a deposition of a second layer 30 of a third material for example silicon nitride or other insulating material such as an oxide with a predetermined and uniform thickness indicated with u201c e u201d preferably the thickness u201c e u201d is nanometric and it is determined by the dimension of the molecule to be hosted controlled up to 1 nm obviously in the case where the third material is an oxide any suitable deposition method to form the second layer 30 can be employed such methods include both by means of effective deposition of the oxide for example by means of u201c cvd oxide u201d control vapor deposition oxide and by means of growth of the oxide itself from the underlying layer for example by means of u201c thermal oxidation u201d technique this second layer 30 is conformably deposited on the surface 12 and on the spacer seed 22 so that it is to be adapted to the underlying topography similarly to what has been described above for the deposition of the first.