A linear light-emitting device (10A, 10E) comprising: a submount substrate comprising a substrate-top surface, wherein a first horizontal direction, a second horizontal direction and a normal direction perpendicular to each other are specified on the substrate-top surface; a plurality of light-emitting diode semiconductor chips disposed on the substrate-top surface of the submount substrate along the first horizontal direction, wherein each of the LED semiconductor chips comprises a chip-upper surface, a chip-lower surface opposite to the chip-upper surface, a plurality of chip-edge surfaces (1231, 1232, 1233, 1234), and a set of electrodes, wherein the chip-edge surfaces (1231, 1232, 1233, 1234) extend between the chip-upper surface and the chip-lower surface, and the set of electrodes is disposed adjacent to the chip-lower surface; a chip-scale packaging structure (13; 13') disposed on the substrate-top surface of the submount substrate and covering the chip-upper surface and/or at least one of the chip-edge surfaces (1231, 1232, 1233, 1234) of each of the LED semiconductor chips, wherein the chip-scale packaging structure (13; 13') comprises a main light-emitting surface, wherein the main light-emitting surface comprises a single, continuous light-emitting surface for all of the plurality of LED semiconductor chips, and wherein the main light-emitting surface and the chip-upper surfaces or the at least one of the chip-edge surfaces (1231, 1232, 1233, 1234) of the LED semiconductor chips covered by the chip-scale packaging structure (13; 13') are disposed opposite and are spaced apart from each other; a reflective structure (14; 14') disposed on the substrate-top surface of the submount substrate, and covering the LED semiconductor chips and the chip-scale packaging structure (13; 13'), but exposing the main light-emitting surface of the chip-scale packaging structure (13; 13'), wherein the reflective structure (14; 14') comprises a single, continuous reflective structure for all of the plurality of LED semiconductor chips; and a reflective layer disposed on the substrate-top surface of the submount substrate, wherein the chip-scale packaging structure (13; 13') is disposed on the reflective layer, characterized in that the reflective layer partially covers the chip-edge surfaces (1231, 1232, 1233, 1234) of each LED semiconductor chip, and that the reflective structure (14; 14') and the reflective layer are configured to form an optical cavity to effectively guide the primary light of the LED semiconductor chips toward the main light-emitting surface of the chip-scale packaging structure (13; 13'). a submount substrate comprising a substrate-top surface, wherein a first horizontal direction, a second horizontal direction and a normal direction perpendicular to each other are specified on the substrate-top surface; a plurality of light-emitting diode semiconductor chips disposed on the substrate-top surface of the submount substrate along the first horizontal direction, wherein each of the LED semiconductor chips comprises a chip-upper surface, a chip-lower surface opposite to the chip-upper surface, a plurality of chip-edge surfaces (1231, 1232, 1233, 1234), and a set of electrodes, wherein the chip-edge surfaces (1231, 1232, 1233, 1234) extend between the chip-upper surface and the chip-lower surface, and the set of electrodes is disposed adjacent to the chip-lower surface; a chip-scale packaging structure (13; 13') disposed on the substrate-top surface of the submount substrate and covering the chip-upper surface and/or at least one of the chip-edge surfaces (1231, 1232, 1233, 1234) of each of the LED semiconductor chips, wherein the chip-scale packaging structure (13; 13') comprises a main light-emitting surface, wherein the main light-emitting surface comprises a single, continuous light-emitting surface for all of the plurality of LED semiconductor chips, and wherein the main light-emitting surface and the chip-upper surfaces or the at least one of the chip-edge surfaces (1231, 1232, 1233, 1234) of the LED semiconductor chips covered by the chip-scale packaging structure (13; 13') are disposed opposite and are spaced apart from each other; a reflective structure (14; 14') disposed on the substrate-top surface of the submount substrate, and covering the LED semiconductor chips and the chip-scale packaging structure (13; 13'), but exposing the main light-emitting surface of the chip-scale packaging structure (13; 13'), wherein the reflective structure (14; 14') comprises a single, continuous reflective structure for all of the plurality of LED semiconductor chips; and a reflective layer disposed on the substrate-top surface of the submount substrate, wherein the chip-scale packaging structure (13; 13') is disposed on the reflective layer, characterized in that the reflective layer partially covers the chip-edge surfaces (1231, 1232, 1233, 1234) of each LED semiconductor chip, and that the reflective structure (14; 14') and the reflective layer are configured to form an optical cavity to effectively guide the primary light of the LED semiconductor chips toward the main light-emitting surface of the chip-scale packaging structure (13; 13').