In this paper, we present both a theoretical evaluation and the fabrication of a novel polymerase chain reaction (PCR) microdevice. This microdevice contains elements for both thermal cycling and fluorescence detection. The proposed device is composed of a reaction chamber with integrated temperature sensor, heaters, p-n diode and optical filter. The advantage of combining these in a single structure is that real time detection of DNA amplification will be possible using a small volume of the PCR solution. The photodiode is covered by a thin film optical filter in order to block out the light which is used to excite the fluorophore dyes. CdS is used for the first time for such a filter and the complete microfabrication process is described.