Verfahren zum Erzeugen einer Grabenisolation in einem Substrat

The method involves initially depositing an oxide layer (112) on a structured layer (100) of the SOI substrate. The oxide layer is then structured around a mask, produced using a photoresist, which will be used to define a following trench production step. The trench (114) is then etched down to the insulation layer (104) of the SOI substrate through use of the mask. The trench is then filled with oxide before a polysilicon layer (124) is deposited on the oxide layer and on the oxide filled trench. The polysilicon layer is then removed from the oxide layer with only a polysilicon covering over the oxide trench being left. The oxide layer is then subsequently removed. The initial oxide layer is initially deposited on the substrate by first depositing a pad oxide layer (108), a nitride layer (110) and a further oxide layer on the front side of the substrate. The nitride layer and the second oxide layer are then removed, the nitride layer being removed from back side of the layer structur e. ADVANTAGE - For ULSI and VLSI integrated CMOS circuit formed on single crystal silicon, e.g. bulk silicon. Simplified process at reduced cost.