The present disclosure provides a light emitting device, including a serially- connected LED array including a plurality of LED cells on a substrate, including a first LED cell, a second LED cell, and a serially-connected LED sub-array intervening the first and second LED cell; a trench between two neighboring sides of the first and the second LED cells; and a protecting structure formed near the trench to prevent the light-emitting device from being damaged by a surge voltage higher than a normal operating voltage. The protecting structure includes a first insulating layer and a second insulating layer formed over the first insulating layer and partially filling in the trench, wherein two ends of the first insulating layer extending outward from the second insulating layer partially covers the top surfaces of the first and the second LED cells.