SEMICONDUCTOR DEVICE AND ITS MANUFACTURING METHOD

PROBLEM TO BE SOLVED: To provide a semiconductor device in which avalanche yield strength is improved and, at the same time, on-resistance is reduced in a semiconductor device like a trench gate type MOSFET based on trench contact technique, and to provide a manufacturing method of the semiconductor device. SOLUTION: The semiconductor device is provided with a first conductivity type semiconductor layer (2), a base region (3) formed in the vicinity of a surface of the layer (2), a source region (4) formed selectively on the base region, a trench (T), a gate insulating layer (7) and a gate electrode (6) which are formed on an inner wall of the trench, and a source electrode (9) connected with the source region. As to the source region, impurity concentration is higher in a part (4a) in contact with the source electrode than both in a part in contact with the gate insulating layer and in a part (4a) in contact with the base region.