the final structure may have a very shallow dimple on top of the filled trench this can be filled and smoothed by cvd or by an additional glassing procedure the depth of the dimple is in the range of 5000 u00e5 or less and can easily be filled or alternatively can be left as is in accordance with the second preferred embodiment of this method the lift off technique is not employed but based on experimental results produces a structure shown in fig3 fig3 is a schematic representation of a sem photograph of a structure having a sio 2 lining on a silicon substrate glassing of sedimented corning glass x760lz without utilizing trichloroethylene is employed followed by firing the glass at 950 u00b0 c for twenty minutes in air the top glass surface may or may not be perfectly flat photoresist leveling and rie planarization may be used to remove the glass layer on top the technique is similar to existing cvd techniques however the surface topography of the glassing ddi results in a much better condition than that of the prior cvd method moreover by utilizing the sedimented glass stress defects around the trench area are removed and mismatch of thermal expansion coefficient is also eliminated a third method utilizes the 34 trichlor 34 technique described in the literature with respect to a new technique of forming a bridge or plug structure on the trench fig4 is a schematic representation of.