a high sensitivity semiconductor photo - electric converter is provided by electrically isolating the gate region of a static induction transistor which exhibits non - saturating current versus voltage characteristic . optically ionized minority carriers are stored in the gate region to control the potential thereof . a semiconductor gate region provided with a insulated gate is very effective to enhance the dynamic range of the converter . non - saturating characteristic enables enlargement of the output current simply by increasing the drain voltage . a high - speed and high sensitivity image pick - up device can be materialized by integrating a multiplicity of the static induction type photo - electric converter elements . a switching transistor may be merged in the gate region of each photo - electric converter element to enhance the operation speed of the image pick - up device .