Provided is a semiconductor laser diode. The semiconductor laser diode includes a first material layer, an active layer, and a second material layer, characterized in that the semiconductor laser diode includes: a ridge waveguide, which is formed in a ridge shape over the second material layer to define a channel defined so that a top material layer of the second material layer is limitedly exposed, and in which a second electrode layer which is in contact with the top material layer of the second material layer via the channel is formed; and a first protrusion, which is positioned at one side of the ridge waveguide and has not less height than that of the ridge waveguide.