Lateral double diffused metal oxide semiconductor device and method of manufacturing the same

A method of manufacturing an LOMOS device which has a source and a drain arranged to be separated from each other on both sides of a substrate with a gate interposed there between, the method comprising:

• implanting first conduction type impurity ions into the first regions of the substrate forming first conduction type impurity regions in the substrate, wherein a second region of the substrate remains undoped and the undoped second region includes a first portion on which the source is to be formed and at least one second portion positioned between the first portion and a on which the drain is to be formed;
• forming an oxide film on the first regions of the substrate through an oxidation process;
• performing an impurity implantation process with the oxide film as an ion implantation mask to implant second conduction type impurity ions into the second region forming a second conduction type impurity region at the first portion and at least one second conduction type impurity ring at the at least one second portion;
• removing the oxide film and performing a thermal process on the semiconductor substrate,
• forming
• i) a first conduction type deep well serving as a drift region of the LOMOS device from the first conduction type impurity region in the substrate,
• ii) a second conduction type well connected to the drift region from the a second conduction type impurity region at the first portion, and
• iii) at least one internal field ring in the drift region from the at least one second conduction type impurity ring at the at least one second portion;
• and then forming a field oxide film on the substrate above the at least one internal field ring.