PURPOSE: To increase the electrostatic breakdown strengh, to reduce the capacity between a gate and a source, and to improve the high frequency characteristic by a method wherein a diffused layer pattern is made as one that a wave form fold is formed along one loop.

CONSTITUTION: A plain pattern of a p diffused layer 3 and an n diffused layer 2 forming the p-n junction is the one that is formed the wave form fold along the one loop (closed curved line). In the protective diode of the patten which the diffused layer making such a junction has the fold along the loop, since the junction length is large, the electrostatic breakdown strength can be obtained largely.