The present disclosure, in some embodiments, relates to an integrated chip. The integrated chip has a channel layer disposed over a substrate and including a first material. An active layer is over the channel layer and includes a second material different than the first material. An isolation structure has a horizontally extending segment that is below the channel layer and one or more vertically extending segments that are directly over the horizontally extending segment. One or more contacts extend through the channel layer and the active layer to contact the one or more vertically extending segments.