| CPC H01L 21/76224 (2013.01) [H01L 21/31155 (2013.01)] | 20 Claims |

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1. A method, comprising:
providing a device stack comprising a buried oxide (BOX) layer in a substrate;
patterning a hardmask over the substrate;
forming a plurality of isolation regions in the device stack, wherein the plurality of isolation regions extend through the BOX layer and the substrate;
forming a well mask over the device stack, wherein an opening through the well mask exposes a first isolation region of the plurality of isolation regions; and
modifying a stress of a material of the first isolation region by implanting the hardmask and the first isolation region of the plurality of isolation regions.
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