are then removed by dissolving the photoresist pattern 5 by a solvent thereby causing the metal layer 7 deposited on the photoresist pattern 5 to 34 lift off 34 leaving on those surfaces of the thin silicon oxide layer 4 under which there are present bodies of heavily n doped silicon 6 portions of the layer 7 of conductive metal separated areas of heavily p doped silicon 8 are then provided between the areas of n doped silicon 6 by boron implantation and drive in the doping concentration of the heavily p doped silicon areas 8 is higher than 10 19 cm 3 to make good ohmic contact to the p type body the resultant structure is shown in fig3 the remaining portions of the first layer of conductive metal 7 are then removed a thin layer of silicon nitride 9 of a thickness of 500 u00e5 1500 u00e5 is then deposited by a cvd chemical vapor deposition process on the layer of silicon oxide 4 a first thick layer 10 of lto low temperature oxide of a thickness of 7000 u00e5 15000 u00e5 is then deposited on the nitride layer 9 by low temperature cvd a second photoresist pattern 11 is then provided on the surface of the first thick layer 10 of lto in a manner so as to expose areas of the first thick layer 10 of lto provided above the center areas of the n doped silicon areas 6 the resultant structure shown in fig4 is then subjected to reactive ion etching to remove portions of the first lto layer 10 and all portions of underlying areas extending to the first epitaxy n doped silicon layer 2 so as to form trenches 12 cutting through in the middle.