A method of isolating semiconductor devices formed on a semiconductor substrate having a silicon on insulator (SOI) layer is provided. The method includes forming at least one shallow trench area on a pad nitride layer deposited on a surface of the SOI layer, wherein the at least one shallow trench area includes an opening for exposing a portion of the SOI layer; applying diblock copolymer material over the pad nitride layer and the at least one shallow trench area; annealing the applied copolymer material to form self-organized patterns; and partially etching the shallow trench area using the diblock copolymer material as an etch mask. A semiconductor structures is also described having an isolation structure formed on a SOI layer of a semiconductor substrate the isolation structure having an oxidized substrate region; and a void region formed on the oxidized substrate region.