The present invention provides a semiconductor device that can achieve both low on-resistance and high withstand voltage, while reducing the device size, improving the manufacturing yield, and reducing the cost. The semiconductor device 1 includes a substrate 5, an epitaxial layer 6 formed on the substrate 5 and formed with a gate trench 11, a gate insulating film 17 formed on the side surface 14 and the bottom surface 15 of the gate trench 11, a gate electrode 20 embedded in the gate trench 11 and opposed to the epitaxial layer 6 with the gate insulating film 17 therebetween, and a source layer 25, a channel layer 26, and a drift layer 27 formed in this order from a first surface to a second surface of the epitaxial layer 6, in which the on-resistance Ron represented by a variable “y” and the withstand voltage Vb represented by a variable “x” functionally satisfy the following relational expression (1): y≤9×10−7x2−0.0004x+0.7001  (1).