A method of manufacturing a substantially planar electronic device comprising a first terminal, a second terminal, and a semiconductor channel providing a current flow path via which current can flow from the first terminal to the second terminal, the method comprising the steps of: providing a first structure comprising a substrate, a layer of semiconductor material supported by the substrate, and a layer of conductor material covering the layer of semiconductor material; processing the first structure to form a second structure comprising said substrate, a first terminal region comprising a first portion of the layer of semiconductor material covered by a first portion of the layer of conductor material, a second terminal region comprising a second portion of the layer of semiconductor material covered by a second portion of the layer of conductor material, a third portion of the layer of semiconductor material not covered by a portion of the layer of conductor material and providing a semiconductor channel connecting the first and second terminal regions, and a plurality of insulative features interrupting the layer of semiconductor material and defining at least a position of the semiconductor channel; forming a layer of photoresist material over the second structure to cover the first and second terminal regions and the third portion of the layer of semiconductor material, and fill the insulative features to form a third structure; exposing the third structure to electromagnetic radiation from a direction such that the first and second portions (52, 53) of the layer of conductor shield overlying portions (62, 63) of the layer of photoresist material from the radiation; removing an exposed portion of the layer of photoresist material to form a window through said layer of photoresist material; depositing dielectric material at least within said window to form a layer of dielectric material filling the insulative features and covering the third portion of the layer of semiconductor material; and removing remaining material (62, 63) of the layer of photoresist material to expose the first and second portions (52, 53) of the layer of conductor material. providing a first structure comprising a substrate, a layer of semiconductor material supported by the substrate, and a layer of conductor material covering the layer of semiconductor material; processing the first structure to form a second structure comprising said substrate, a first terminal region comprising a first portion of the layer of semiconductor material covered by a first portion of the layer of conductor material, a second terminal region comprising a second portion of the layer of semiconductor material covered by a second portion of the layer of conductor material, a third portion of the layer of semiconductor material not covered by a portion of the layer of conductor material and providing a semiconductor channel connecting the first and second terminal regions, and a plurality of insulative features interrupting the layer of semiconductor material and defining at least a position of the semiconductor channel; forming a layer of photoresist material over the second structure to cover the first and second terminal regions and the third portion of the layer of semiconductor material, and fill the insulative features to form a third structure; exposing the third structure to electromagnetic radiation from a direction such that the first and second portions (52, 53) of the layer of conductor shield overlying portions (62, 63) of the layer of photoresist material from the radiation; removing an exposed portion of the layer of photoresist material to form a window through said layer of photoresist material; depositing dielectric material at least within said window to form a layer of dielectric material filling the insulative features and covering the third portion of the layer of semiconductor material; and removing remaining material (62, 63) of the layer of photoresist material to expose the first and second portions (52, 53) of the layer of conductor material.