A semiconductor device having a active layer comprising crystalline silicon, said active layer comprising a first layer comprising crystalline silicon formed on an insulating surface and a second layer comprising crystalline silicon formed on said first layer, wherein said first layer contains...http://www.google.co.uk/patents/US5773847?utm_source=gb-gplus-sharePatent US5773847 - Semiconductor device having an active layer with separate layers where one of the layers acts as crystal nuclei for the other 
