Abstract: Disclosed is a semiconductor device which comprises a substrate, an insulating film formed at a predetermined region in the substrate or on the main surface of the substrate, a polycrystalline semiconductor layer formed on at least the insulating film, a single crystal semiconductor layer formed on at least the polycrystalline semiconductor layer, an isolation region formed to extend from the top main surface of the single crystal semiconductor layer to at least the surface of the insulating film, through the polycrystalline semiconductor layer, to electrically isolate a portion formed in the single crystal semiconductor layer surrounded by the isolation region from another portion formed in the single crystal semiconductor layer and not surrounded by the isolation region, at least a semiconductor device formed within the portion surrounded by the isolation region.

Abstract: A grain oriented electromagnetic steel sheet having a very low iron loss is obtained by subjecting a surface of base metal in the sheet after finish annealing to a particular mechanical polishing and has a surface roughness having a center-line average roughness of not more than 0.3 .mu.m after the polishing and the number of abrasive grains embedded in a layer just beneath polished surface of not more than 20,000 grains/cm.sup.2.