Method of making a semiconductor device having trenches

Providing self aligned contacts in a semiconductor device arrangement, comprises etching trenches in substrate through photo resist mask of silicon nitride deposited on oxide layer and forming gate oxide layer on walls of trenches; applying polysilicon to fill trenches and to cover the surface of the mask of silicon nitride; and removing polysilicon from the surface of the mask and applying a photoresist mask to cover a location of the gate bus. Providing self aligned contacts (331) in a semiconductor device arrangement, comprises etching trenches in substrate through photo resist mask of silicon nitride deposited on oxide layer and forming gate oxide layer on walls of trenches; applying polysilicon to fill the trenches and to cover the surface of the mask of silicon nitride; removing polysilicon from the surface of the mask of silicon nitride and applying a photoresist mask to cover a location of the gate bus; and recessing polysilicon plugs formed in trenches that are in an active area to form recesses above the polysilicon plugs.