SEMICONDUCTOR DEVICE AND METHOD OF MANUFACTURING THE SAME

PROBLEM TO BE SOLVED: To protect a transistor when a high voltage is applied to its drain, without increasing the capacitance near the drain. SOLUTION: The semiconductor device is provided with a gate electrode 4, which is formed on a silicon semiconductor substrate 1 via a gate oxide film 5 and a pair of N+ type diffusion layers 7a, 7b which are formed in the surface region of the substrate 1 on both sides of the gate electrode 4. An N-type diffusion layer which protrudes toward the lower layer from the bottom of the layer 7b is formed in the prescribed region of the layer 7b on the side of the drain.