Nitride semiconductor device

A nitride semiconductor device comprising:

• an n-type nitride semiconductor layer;
• a p-type nitride semiconductor layer;
• and
• an active layer formed between the n-type and p-type nitride semiconductor layers, the active layer comprising a plurality of quantum well layers and at least one quantum barrier layer deposited alternately with each other,
• wherein the active layer comprises a first quantum well layer, a second quantum well layer formed adjacent to the first quantum well layer toward the p-type nitride semiconductor layer and having a zero quantum level higher than a zero quantum level of the first quantum well layer, and a tunneling quantum barrier layer formed between the first and second quantum well layers and having a thickness enabling a carrier to be tunneled therethrough,
• wherein the first quantum well layer has the same band gap energy as that of the second quantum well layer.