A bonded SOI wafer and a method for forming a bonded SOI wafer are provided. According to the disclosed method, a first semiconductor wafer is provided, having a first dielectric layer disposed at an outer surface of the first wafer and a plurality of dielectric filled trenches extending from the outer surface inwardly into the semiconductor. The outer surface of the first wafer is bonded to the outer surface of a second semiconductor wafer to form a bonded wafer having a bulk semiconductor region, a buried dielectric layer overlying the bulk semiconductor region, and a semiconductor-on-insulator layer overlying the buried dielectric layer, with the dielectric filled trenches extending upwardly from the buried dielectric layer into the semiconductor-on-insulator layer. The thickness of the semiconductor-on-insulator layer is then reduced until uppermost surfaces of at least some of the dielectric filled trenches are at least partially exposed.