| 摘要 |
PURPOSE:To simplify the flattening step of a polycrystalline semiconductor layer accumulated on a groove of U-shaped section by etching with 2-layer masks of different etching velocities. CONSTITUTION:A U-shaped groove 2 is formed on an Si substrate 1, an SiO2 film 3 is formed on the surface, and a polysilicon layer 4 is then accumulated. Then, a PSG film 11 and an Si3N4 film 12 is formed, and the polysilicon is etched. At this time etchant is selected to accelerate the side etching of the film 11. Thus, the etching of the polysilicon is sequentially advanced as shown by broken lines 1-5, and the polysilicon is flattened by one etching. |
