Abstract: A semiconductor light emitting device is disclosed, which comprises: a substrate having a first surface and a second surface; a first semiconductor conductive layer is disposed on the first surface of the substrate; an insert layer is disposed on the first semiconductor conductive layer; an active layer is disposed on the insert layer; a second semiconductor conductive layer is disposed on the active layer; a first electrode is disposed on the second semiconductor conductive layer; and a second electrode is disposed on the second surface of the substrate, in which the electric of the second electrode is opposite to that of the first electrode.