Semiconductor device and method of manufacturing the same

A method of manufacturing a semiconductor device including an active part in which a power MOSFET is formed and an outer peripheral part formed around the active part, comprising the steps of:

• (a) forming, over a substrate of a first conductivity type, an epitaxial layer of a second conductivity type different from the first conductivity type;
• (b) forming, in the epitaxial layer in the active part, a plurality of first trenches, each of which has a first depth from an upper face of the epitaxial layer, and which extends in a first direction in plan view with a first interval provided therebetween in a second direction orthogonal to the first direction in plan view;
• (c) after the step (b), inclinedly ion-implanting a first impurity ion of the first conductivity type into the epitaxial layer from a side wall of the first trench;
• (d) after the step (c), providing a heat treatment to diffuse the first impurity ion into the whole of the epitaxial layer between the adjacent first trenches;
• (e) after the step (d), inclinedly ion-implanting a second impurity ion of the second conductivity type into the epitaxial layer from a side wall of the first trench;
• (f) after the step (e), providing a heat treatment to diffuse the second impurity ion so as not to spread into the whole of the epitaxial layer between the adjacent first trenches;
• and
• (g) after the step (f), embedding a first insulating film inside the first trench.