The invention provides an integrated semiconductor device (100) for detecting fluorescent tags, comprising a first layer (101) comprising a detector element (107), a second layer (102) located on top of the first layer (101) and comprising a rejection filter, a third layer (103) located on top of the second layer (102) and being fabricated from a dielectric material, a fourth layer (104) located on top of the third layer (103) and comprising an optical waveguide, and furthermore a fifth layer located on top of the fourth layer comprising a microfluidic channel (106). The optical waveguide is configured and positioned such that the micro-fluidic channel (106) is illuminated with an evanescent tail of excitation light guided by the optical waveguide. The rejection filter is positioned such that fluorescence from activated fluorescent tags present on top of the fourth layer (104) is filtered before falling onto the detector element (107). The rejection filter is configured to reject the wavelength range of the excitation light and configured to transmit the wavelength range of fluorescence from the activated fluorescent tags towards the detector element (107).