The present disclosure provides a device, such as a FET sensing cell, which includes a first dielectric layer over a substrate, an active layer over the first dielectric layer, a source region in the active layer, a drain region in the active layer, a channel region in the active layer situated between the source region and the drain region, a sensing film over the channel region, a second dielectric layer over the active layer, wherein an opening is formed in the second dielectric layer and the sensing film is located within the opening, a first electrode located within the second dielectric layer and a fluidic gate region located over the second dielectric layer and extending into the opening. The present disclosure also provides a method for improving the sensitivity of a device by adjusting a sensing value.