A semiconductor device package comprising: a substrate; a first lead frame and a second lead frame disposed on the substrate; a light emitting semiconductor device electrically connected to the first and second lead frames (20, 30); a reflective layer disposed on the substrate and configured to reflect light emitted from the light emitting semiconductor device; and a lens disposed on the substrate and configured to cover the light emitting semiconductor device, the reflective layer, the first and second lead frames (20, 30) wherein the first lead frame includes: a first lead electrode portion electrically connected to the light emitting semiconductor device; an edge portion disposed on an edge of the substrate and surrounding the first lead electrode portion and the second lead frames; and an extension portion configured to connect the edge portion to the first lead electrode portion, wherein the lens includes a convex portion disposed on a central portion of the lens and a flat portion configured to surround the convex portion, the flat portion having a top surface extending in a plane perpendicular to the thickness direction of the substrate, wherein the reflective layer comprises a dam portion disposed on the edge portion of the first lead frame, and surrounding the light emitting semiconductor device, wherein the dam portion has one surface facing the light emitting semiconductor device and the other surface opposite to the one surface, and the one surface has a curvature and the other surface has a flat surface, wherein a height of the dam portion in a thickness direction of the substrate is 1/3 times to two times a height of the light emitting semiconductor device, and is lower than that of the flat portion of the lens, wherein the heights (h1,h2) are defined with respect to the upper surface of the first and second lead frames (20,30). a substrate; a first lead frame and a second lead frame disposed on the substrate; a light emitting semiconductor device electrically connected to the first and second lead frames (20, 30); a reflective layer disposed on the substrate and configured to reflect light emitted from the light emitting semiconductor device; and a lens disposed on the substrate and configured to cover the light emitting semiconductor device, the reflective layer, the first and second lead frames (20, 30) wherein the first lead frame includes: a first lead electrode portion electrically connected to the light emitting semiconductor device; an edge portion disposed on an edge of the substrate and surrounding the first lead electrode portion and the second lead frames; and an extension portion configured to connect the edge portion to the first lead electrode portion, wherein the lens includes a convex portion disposed on a central portion of the lens and a flat portion configured to surround the convex portion, the flat portion having a top surface extending in a plane perpendicular to the thickness direction of the substrate, wherein the reflective layer comprises a dam portion disposed on the edge portion of the first lead frame, and surrounding the light emitting semiconductor device, wherein the dam portion has one surface facing the light emitting semiconductor device and the other surface opposite to the one surface, and the one surface has a curvature and the other surface has a flat surface, wherein a height of the dam portion in a thickness direction of the substrate is 1/3 times to two times a height of the light emitting semiconductor device, and is lower than that of the flat portion of the lens, wherein the heights (h1,h2) are defined with respect to the upper surface of the first and second lead frames (20,30). a first lead electrode portion electrically connected to the light emitting semiconductor device; an edge portion disposed on an edge of the substrate and surrounding the first lead electrode portion and the second lead frames; and an extension portion configured to connect the edge portion to the first lead electrode portion, wherein the lens includes a convex portion disposed on a central portion of the lens and a flat portion configured to surround the convex portion, the flat portion having a top surface extending in a plane perpendicular to the thickness direction of the substrate, wherein the reflective layer comprises a dam portion disposed on the edge portion of the first lead frame, and surrounding the light emitting semiconductor device, wherein the dam portion has one surface facing the light emitting semiconductor device and the other surface opposite to the one surface, and the one surface has a curvature and the other surface has a flat surface, wherein a height of the dam portion in a thickness direction of the substrate is 1/3 times to two times a height of the light emitting semiconductor device, and is lower than that of the flat portion of the lens, wherein the heights (h1,h2) are defined with respect to the upper surface of the first and second lead frames (20,30).