PURPOSE: To increase the distance between both electrode metals of a constant-current diode by isolating and forming part of a diffused layer becoming a gate region and a diffused layer becoming a source region so as to alternately intrude in a circumferential direction to each other and forming a stepwise difference between a connecting electrode metal on the region and a drain electrode metal.

CONSTITUTION: On a P type semiconductor substrate 21 is grown an N type epitaxial layer 22 having a flat raised top shape, in the layer 22 are further formed an annular P type diffused layer 23 becoming a gate region and an N type diffused layer 24 becoming a source region, and at the center is formed an N type diffused layer 24 becoming a drain region. A plurality of rectangular P type diffused layers 23a are formed at the prescribed interval circumferentially on the layer 23, thereby forming a P type diffused layer 23b passing through the substrate 21 connected to the layer 23a. An N type diffused layer 25 formed in the adjacent region formed with the layers 23, 23a and 23b is formed of an N type diffused layer 24a corresponding to the layers 23a, 23b and an N type diffused layer 24b extending to the substrate 21. In this manner, an electrode metal 27 and an annular connecting metal 28 are formed through an insulating layer 26 such as an SiO2 on the substrate 21, the layers 24b, 23b, thereby completing a constant- current diode having stepwise difference between both electrodes.