This invention provides a photo-FET, in which a FET part and photodiode part are stacked, and the FET part and photodiode part are optimized independently in design and operational bias conditions. The semiconductor layer serving as a photo-absorption layer (41) is formed on the cathode semiconductor layer (10) of a photodiode part (50). An electron barrier layer (40) with a wider bandgap semiconductor than a photo-absorption layer (41), which also serves as an anode layer of a photodiode part (50), is formed on a photo-absorption layer (41). The channel layer (15) which constitutes the channel regions of the FET part is formed with a narrower bandgap semiconductor than an electron barrier layer (40) on an electron barrier layer (40). The hole barrier layer (16) with a bandgap wider than the semiconductor which constitutes a channel layer (15) is formed on a channel layer (15). The source electrode (30) and drain electrode (32) which are separated each others, are formed on a hole barrier layer (16). The holes injected into the channel layer (15) by light illumination through the electron barrier layer (40) from the photo-absorption layer (41) are confined with the hole barrier layer (16). And the electrons in a channel layer (15) are confined with the electron barrier layer (40) into the channel layer (15), respectively.