Semiconductor device, light emitting device using the same, and light emitting device package including the same

A semiconductor device is disclosed. The semiconductor device includes a silicon substrate, an initial buffer layer disposed on the silicon substrate, a transition layer disposed on the initial buffer layer, and a device structure disposed on the transition layer, wherein the transition layer includes at least one of Al x Ga 1-x N (where 0 < x < 1) layers disposed on the initial buffer layer and an inserted buffer layer disposed at least one of between the AL x Ga 1-x N layers, at a lower end portion of the transition layer, or at an upper end portion of the transition layer.