A method of forming a semiconductor device, including forming a first semiconductor layer on a semiconductor substrate, the first semiconductor layer being of the same dopant type as the semiconductor substrate, the first semiconductor layer having a higher dopant concentration than the semiconductor substrate, increasing the porosity of the first semiconductor layer, first annealing the first semiconductor layer at a temperature of at least 1050° C., forming a second semiconductor layer on the first semiconductor layer and separating the second semiconductor layer from the semiconductor substrate by splitting within the first semiconductor layer.