Embodiments herein present a method for forming a poly filled substrate contact on a SOI structure. The method forms an insulator on a substrate and forms a substrate contact hole within the insulator. The insulator surface level is higher than final structure. Next, a poly overfill is performed, comprising filling the substrate contact hole with polysilicon and covering the insulator with the polysilicon. Specifically, the thickness of the polysilicon is greater than the size of the substrate contact hole. Following this, the polysilicon is etched, wherein a portion of the polysilicon is removed, and wherein the substrate contact hole is left partially filled with the polysilicon. Further, the etching of the polysilicon forms a concave recess within a top portion of the polysilicon. The etching of said polysilicon does not contact the substrate. The excess of insulator is polished off to the desired level.