For some photonic applications, it is desirable to decrease the thickness of TMDC devices from multilayers to bi-or even monolayers, e.g. to increase the photoluminescence quantum yield. However, for the most widely studied TMDC, MoS2, Tang et al. have revealed that the speed of photodetection decreases by several orders of magnitude when approaching bi-or monolayer thickness. This is the result of persistent photocurrents due to interface trap states ultra-thin WSe2 device using the same geometries as for the 230 MHz multilayer photodetector (see Fig. ). From the optical characterization in Fig. , we infer that this photodetector consists exclusively of mono-and bilayers of WSe2 within the channel. While a reliable power spectrum cannot be obtained due to the relatively weak absorption and photocurrent signal, we obtain a fall time of 19 ns in response to a square pulse (Fig. ), demonstrating that the speed of WSe2 photodetectors is much more robust against surface trap states, in stark contrast to MoS2. We attribute the remaining speed difference compared to our champion multilayer WSe2 device to the higher photoresistance due to the weaker absorption, which increases the RC time.