METHOD OF FLATTENING NONCONFORMAL FILM

PROBLEM TO BE SOLVED: To produce a substantial plane where recessed transformation of wide space is reduced, by performing CMP polishing on a nonconformal layer accumulated on complicated landform comprising narrow parts accompanied with narrow gaps, wide parts, and wide gaps. SOLUTION: A nonconformal layer 160 is made on the surface of a substrate 101. Because of the nonconformality of this layer 160, thickness on the surface of a wide active region 112 is thicker than the thickness of a narrow active region 110. Polysilicon (poly) is accumulated on the surface by CVD. A conformal poly layer arises on the nonconformal layer 160 by CVD. The poly layer is flattened selectively by CMP to an oxide. For the CMP polishing, the protuberance of polysilicon is polished first, and the surface of polysilicon is flattened gradually as the material is removed from there. CMP is continued until the surface of the oxide layer 160 in the protuberance region is exposed and a flat top 179 arises.