A semiconductor integrated circuit including therein a plurality of active devices (44a, 44b) comprises a semiconductor substrate (22), a first buffer layer (24) on the substrate, a second buffer layer (26) provided on the substrate and incorporating therein defects with a concentration level substantially larger than the concentration level of the defects in the first buffer layer; a device layer (36) provided on the second buffer layer and being provided with the active devices, and a plurality of unconductive, device isolation regions (38) formed between the active devices such that the device isolation region extends from an upper surface of the device layer toward the substrate at least beyond a lower surface of the device layer.