To provide a method of manufacturing an insulated gate field effect transistor, which is capable of easily improving it in characteristics and reliability and ensuring the degree of freedom of design for it, and to provide an insulated gate field effect transistor which has a source/drain structure and is suitable for ensuring superior characteristics and reliability.

The method of manufacturing the insulated gate field effect transistor comprises a first process of forming a sacrificial layer 7 on a semiconductor 4, second process of forming first source/drain regions 8 in the semiconductor 4 by implantation of ions as the sacrificial layer 7 is used as a mask, third process of covering the sacrificial layer 7 and its vicinity with a thick insulating film 9, fourth process of exposing the top surface of the sacrificial layer 7 and removing the sacrificial layer 7, fifth process of forming a gate insulating film 10 on the surface of the semiconductor 4 where the sacrificial layer 7 has been removed, and sixth process of forming a level difference by the use of the gate insulating film 10 and the thick insulating film 9, seventh process of forming a gate electrode on each side face of the level difference, and eight process of forming a second source/drain region 12 (shown in Figure 4).