Patent ID: 7939410

Claim:
A method of manufacturing a semiconductor device, the method comprising the steps of: forming a first conductive-type buried layer in a semiconductor substrate and forming a first conductive-type drift area on the first conductive-type buried layer; forming a gate insulating layer and gate electrodes by selectively removing the first conductive-type drift area; forming a first oxide layer on the semiconductor substrate including the gate electrodes; implanting second conductive-type impurity ions into the semiconductor substrate including the first oxide layer; forming a nitride layer on the first oxide layer; forming a second conductive-type well by diffusing the second conductive-type impurity ions and simultaneously forming a second oxide layer on the nitride layer; removing the nitride layer and the second oxide layer from the first oxide layer; forming a thin oxide layer by partially removing the first oxide layer; forming first conductive-type source areas at sides of each gate electrode; forming a dielectric layer on the thin oxide layer; forming a trench by selectively etching the dielectric layer and the thin oxide layer; forming a source contact in the trench; and forming a drain electrode layer electrically connected with the first conductive-type buried layer.