PURPOSE: To flatten and smooth a substrate surface by forming and baking a resin layer after etching a baked resin layer.
CONSTITUTION: On a semiconductor substrate 101, resin(polyimide) 102 is formed by a spin coater and baked at 200°C for one hour to be softened. Then, the substrate is etched by O 2 plasma and the top of a projecting part is completely exposed. At this time, the resin 102 in a recessed part remains 1.6μm below the top of the projecting part. A resin layer is formed on the substrate 101 and the level difference of 1.6μm is filled. Then, the layer is baked to be flatten allowing 0.2μm level difference. Thus, the smooth substrate surface is flattened.