A semiconductor device (20, 21, 22), including: a channel region (4) of a first conductivity type formed at a surface layer portion of a semiconductor substrate (1); a source region (25) of a second conductivity type which is different from the first conductivity type, the source region (25) being formed at a rim of a trench (17) having a depth sufficient to penetrate through the channel region (4); a drain region (2) of the second conductivity type formed at a region adjacent to a bottom of the trench (17); a gate insulating film (13) formed along an inner side wall of the trench (17); a gate electrode (26, 36) arranged in the trench (17) so as to be opposed to the channel region (4) with the gate insulating film (13) interposed therebetween; a conductive layer (37, 40, 40a, 40b) formed in the trench (17) so as to be nearer to the drain region (2) than the gate electrode (26, 36); and an insulating layer (15) surrounding the conductive layer (37, 40, 40a, 40b) to electrically insulate the conductive layer (37, 40, 40a, 40b) from the gate electrode (26, 36) and the drain region (2).