The present disclosure relates to an integrated chip having an integrated bio-sensor having horizontal and vertical sensing surfaces. In some embodiments, the integrated chip has a sensing device disposed within a semiconductor substrate. A back-end-of the line (BEOL) metallization stack with a plurality of metal interconnect layers electrically coupled to the sensing device is arranged within an inter-level dielectric (ILD) layer overlying the semiconductor substrate. A sensing well is located within a top surface of the ILD layer. The sensing well has a horizontal sensing surface extending along a top surface of a first one of the plurality of metal interconnect layers and a vertical sensing surface extending along a sidewall of a second one of the plurality of metal interconnect layers overlying the first one of the plurality of metal interconnect layers. The use of both horizontal and vertical sensing surfaces enables more accurate sensing.