MANUFACTURE OF SEMICONDUCTOR DEVICE

PURPOSE:To shorten the time required for forming a U-groove by etching by providing processes for selectively removing an oxide film from the bottom of the U-groove, for filling the U-groove with a material containing an impurity of the same conductivity as that of the substrate into which the U-groove is formed, and for diffusing the impurity of the same conductivity as that of the substrate from the material filling up the U-groove into the substrate at the bottom section of the U-groove. CONSTITUTION:A U-groove 5 having a depth reaching a P-type substrate is formed by an anisotropic dry etching technique. In order to remove a layer in the U-groove damaged at the time of the etching, oxidation is performed and an oxide film 6 is formed. The oxide film 6 is removed by using an etching liquid of a hydrofluoric acid type. At the time of removing the film 6, a mask oxide film 4 used at the time of forming the U-groove 5 by etching is left under the same condition. Another oxide film 8 is again formed in the U-groove 5 and an opening 10 is formed by only removing the bottom section of the film 8 by an anisotropic oxide film dry etching technique. Then the U-groove 5 is filled up with a borosilicate glass (BSG) film 11 containing boron which is a Ptype impurity. By diffusing the boron from the film 11 into the substrate by performing appropriate heat treatment, a channel stopper layer 7 is selectively formed at the bottom section of the U-groove 5 only. Finally, the surface of the U-groove is flattened.