Patent ID: 9397167
Filing Date: 2016-07-19
CPC Classification: H01L

Claim Text:
1. A nitride semiconductor device comprising: a silicon substrate having a major surface; a stacked multilayer unit formed on the major surface of the silicon substrate, the stacked multilayer unit including N number of buffer layers stacked in a stacking direction perpendicular to the major surface, the buffer layers including a nitride semiconductor, N being not less than two and not more than nine, the buffer layers including an i-th buffer layer (i being an integer of 1 or more and less than N), and an (i+1)-th buffer layer provided on the i-th buffer layer, the (i+1)-th buffer layer being in contact with the i-th buffer layer, the i-th buffer layer having an i-th lattice length Wi in a first direction parallel to the major surface, the (i+1)-th buffer layer having an (i+1)-th lattice length W(i+1) in the first direction, and a relation that 0.003≦(W(i+1)−Wi)/Wi≦0.008 being satisfied for all the buffer layers; a silicon-containing unit provided on the stacked multilayer unit and containing silicon, the silicon-containing unit being in contact with the stacked multilayer unit; an upper layer unit provided on the silicon-containing unit and including a nitride semiconductor wherein the upper layer unit includes the functional layer includes an impurity-containing layer containing an impurity, and an impurity concentration in the impurity-containing layer is higher than an impurity concentration in the upper buffer layer, the upper layer unit further includes an intermediate layer provided between the upper buffer layer and the functional layer, the intermediate layer includes an Al composition ratio of the second layer is lower than an Al composition of the first layer, the intermediate layer further includes a third layer including a nitride semiconductor including Al and provided between the first layer and the second layer, and an Al composition ratio of the third layer is lower than the Al composition ratio of the first layer and higher than the Al composition ratio of the second layer.