Abstract: A semiconductor device with multilayer wirings can be produced with high yield by applying a liquid source for silicate film to a surface of a chemically vapor deposited insulating layer placed on a surface of the semiconductor substrate in order to provide a smoothed surface. After solidification of the liquid source, the substrate is subjected to a controlled etching to leave the same contour as the one of the smoothed surface on the resultant surface. An upper wiring layer is placed on the resultant smoothed surface in contact with a lower wiring layer through the insulating layer thereby decreasing disconnections in the upper wiring layer which could easily be caused by steep edges existing on an insulating surface layer of a conventional device.