According to the present invention, there is provided a semiconductor device having, a semiconductor substrate having a surface on which an insulating layer is formed, a first-conductivity-type first semiconductor layer formed on the insulating layer and having a first impurity concentration, a first-conductivity-type second semiconductor region formed in the first semiconductor layer from a surface of the first semiconductor layer to a surface of the insulating layer, and having a concentration higher than the first impurity concentration, a second-conductivity-type third semiconductor region formed in the first semiconductor layer from the surface of the first semiconductor layer to the surface of the insulating layer with a predetermined distance between the second and third semiconductor regions, and having a second impurity concentration, a second-conductivity-type fourth semiconductor region formed in a surface portion of the second semiconductor region, and having a concentration higher than the second impurity concentration, an insulating film formed over the surfaces of the first, second, third, and fourth semiconductor layers, and a control electrode formed on the insulating film, wherein a junction of first and second conductivity types formed between the first semiconductor layer and the third semiconductor region is positioned below the control electrode, or below an end portion, on a side of the third semiconductor region, of the control electrode, via the insulating film.