Abstract: A method is provided for making a semiconductor device which includes the steps of forming a first insulating layer on the surface of a semiconductor layer having a given conductivity type, forming an opening in the insulating layer and forming a diffusion region of a conductivity type opposite to that of the given conductivity type at the surface of the semiconductor layer to provide a P-N junction below the surface of the semiconductor layer. A trench is then formed along a given axis in the semiconductor layer having a sidewall passing through the opening and through the P-N junction. A second layer of insulation is formed on the sidewall of the trench, on the first insulating layer and through the opening onto the diffusion region. The second layer of insulation is etched in the direction of the given axis until substantially all of the second layer of the insulation is removed from the opening, and an electrical contact is formed on the diffusion region within the opening.