We systematically investigated photoresponse flipping of silicon nanowire (SiNW) metal oxide semiconductor field effect transistor (MOSFET) incorporated with poly(3-hexylthiophene) (P3HT). This phenomenon can be controlled by spatial charge polarization in P3HT film simply by its thickness, which results in opposite virtual gating effect in SiNW channel. With several layers of P3HT (~10 nm), photoresponse of transistor-P3HT hybrid system was occurred within roughly a second. However, P3HT film is in bulk regime (> 100 nm), response time was largely elongated to ~103 seconds and photoresponse was occurred with opposite sign. This seems to be ascribed to the generated holes drift by built in potential in P3HT film. The observations could be understood by analysis using band diagram and three-level system by two photon absorption process. First, roughly several tens of percentages of excited electrons are transited to the SiNW channel side. Then, very low transit probability of exited electrons by second absorption of incident photons (~ 10-3 ％) can be overcome by sufficient number of incident photons at experimental condition. Using our observations, by selecting band structure of decorating material on the host SiNW channel and its thickness, cut-off detector energy and polarity of photoresponse can be easily designed. Our findings can be applicable to the next generation COMS technology incorporated with light illumination.