A diode is provided which includes a first-conductivity-type cathode layer, a
first-conductivity-type
drift layer placed on the cathode region and having a lower concentration than
the cathode layer, a generally ring-like second-conductivity-type ring region formed
in the drift layer, second-conductivity-type anode region formed in the drift layer
located inside the ring region, a cathode electrode formed in contact with the
cathode layer, and an anode electrode formed in contact with the anode region,
wherein the lowest resistivity of the second-conductivity-type anode region is
at least 1/100 of the resistivity of the drift layer, and the thickness of the
anode region is smaller than the diffusion depth of the ring region.