Semiconductor device with sensor and manufacturing method thereof

A method of manufacturing a semiconductor device, comprising:

• providing a substrate comprising devices therein, the substrate having a front side and a rear side opposite to the front side;
• disposing an interconnect on the front side and electrically coupling the interconnect to the devices;
• and
• forming a sensor over the substrate and in the interconnect, the sensor comprising a sensing element and a reference element disposed in a topmost layer of the interconnect and exposed therefrom, wherein the sensing element is electrically coupled to a first device of the devices and comprises a first gate electrode, a first semiconductor layer disposed over the first gate electrode, a pair of first source/drain regions vertically disposed over the first semiconductor layer, and a first sensing layer disposed on the first semiconductor layer and over the first gate electrode, and wherein the reference element is laterally spaced from the sensing element and electrically coupled to a second device of the devices, and the reference element comprises a second gate electrode, a second semiconductor layer disposed over the second gate electrode, a pair of second source/drain regions vertically disposed over the second semiconductor layer, and a second sensing layer disposed on the second semiconductor layer and over the second gate electrode.