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Abstract

A high withstand voltage insulated gate N-channel field effect transistor has a P-type semiconductor substrate and an N-type epitaxial layer formed on the semiconductor substrate. An N-type source region having a high concentration is formed on the epitaxial layer. An N-type drain region having a high concentration is formed on the epitaxial layer and is spaced-apart from the source region. A channel forming region is disposed between the source region and the drain region. A gate insulating film is disposed over the source and drain regions and the channel forming region. A gate electrode is formed through the channel forming region and the gate insulating film. An N-type low concentration region is formed between the drain region and the channel forming region. A second insulating film is formed on the low concentration region and has a thickness greater than that of the gate insulating film. A P-type buried layer is formed in a boundary region between the semiconductor substrate and the epitaxial layer and below the source region, the drain region, the channel forming region, and the second insulating film. A P-type well layer is formed in a region under the source region and the channel forming region and is formed in a part of a region under the second insulating film so as to surround the drain region.

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First Claim