A semiconductor device disclosed in an embodiment comprises: a light emitting unit comprising a light emitting structure layer which has a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer; and a sensor unit disposed on the light emitting unit, wherein the sensor unit comprises: a sensing material changing in resistance with light emitted by the light emitting unit; a first sensor electrode comprising a first pad portion and a first extension part extending from the first pad portion and contacting the sensing material; and a second sensor electrode comprising a first pad portion and a second extension part extending toward the first extension part from the second pad portion and contacting the sensing material. The sensor unit senses an external gas in response to the light generated from the light emitting unit.