PURPOSE: To provide a semiconductor device which has a structure such that the degree of integration can be raised and the area of a source is decreased, according to the development of a fine processing technology.

CONSTITUTION: A first group of grooves 152-154, which reach the surface of a substrate 1, are made, along the side faces of isolating regions 21, respectively, and the isolating regions 21 contact with a group of grooves 152, 153, and 155, respecitively, and a takeout region 23 contacts with the groove 153. Furthermore, a second groove 154 is made between the takeout region 23 and a back gate region 39, and the takeout region 23, the back hate region 39, and the source region 45 contact with the groove 154, respectively. A gate electrode 33 is made inside the groove 154, according to the molded part of the back gate region 39, and a channel 63 is made along the side face of the groove 154. According to this constitution, the groove becomes a protective wall against the lateral diffusion of each region, so the increase of the area by the lateral diffusion do not occur. Furthermore, since the channel 63 becomes vertical to the substrate 1, the area of a source region 45 can be reduced.