Patent ID: 8330184

Claim:
A bidirectional voltage-regulator diode, comprising: a first semiconductor layer of a first conductivity type formed on an inner surface of a first recess formed in a first surface of a semiconductor substrate of the first conductivity type so as to generate a second recess smaller than the first recess and having a first impurity concentration lower than an impurity concentration of the semiconductor substrate; a second semiconductor layer of a second conductivity type formed on the inner surface of the second recess so as to generate a third recess smaller than the second recess and having a second impurity concentration; a third semiconductor layer of the second conductivity type formed on the inner surface of the third recess so as to generate a fourth recess smaller than the third recess and having a third impurity concentration higher than the second impurity concentration; a fourth semiconductor layer of the second conductivity type formed on the inner surface of the fourth recess so as to generate a fifth recess smaller than the fourth recess and having a fourth impurity concentration lower than the third impurity concentration; a fifth semiconductor layer of the first conductivity type formed on the inner surface of the fifth recess so as to generate a sixth recess smaller than the fifth recess and having a fifth impurity concentration; a first electrode electrically connected to the fifth semiconductor layer; and a second electrode formed on a second surface opposite to the first surface of the semiconductor substrate.