Silicon on insulator with highly uniform top Si is fabricated by co-implantation of H+ and He+ ions.Compared with the conventional ion-slicing process with H implantation only,the co-implanted specimens whose He depth is deeper than H profile have the top Si layer with better uniformity after splitting.In addition,the splitting occurs at the position that the maximum concentration peak of H overlaps with the secondary concentration peak of He after annealing.It is suggested that the H/He co-implantation technology is a promising approach for fabricating fully depleted silicon on insulator.