US PATENT SUBCLASS 257 / 647
.~.~ Insulating layer recessed into semiconductor surface (e.g., LOCOS oxide)

Current as of: June, 1999
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257 /   HD   ACTIVE SOLID-STATE DEVICES (E.G., TRANSISTORS, SOLID-STATE DIODES)

629  DF  WITH MEANS TO CONTROL SURFACE EFFECTS {4}
632  DF  .~ Insulating coating {8}
647.~.~ Insulating layer recessed into semiconductor surface (e.g., LOCOS oxide) {1}
648  DF  .~.~.~> Combined with channel stop region in semiconductor

DEFINITION

Classification: 257/647

Insulating layer recessed into semiconductor surface (e.g., LOCOS oxide):

(under subclass 632) Subject matter wherein the insulating layer is recessed into the semiconductor surface.

(1) Note. This type of recessed insulator may typically be LOCOS (Local Oxidation of Silicon) oxide, which is formed by oxidizing the silicon surface in areas not covered by an oxidation resistant mask, so that oxide is formed which is recessed into the semiconductor by approximately 1/2 of its thickness due to consumption of silicon to form the silicon oxide. LOCOS oxide may also be recessed fully to be substantially flush with the surface (except in areas at the edge of the oxide, wherein ridges known as "birdheads" (due to their shape) occur, which taper off to small thickness oxide portions in areas protected by the oxidation resistant mask (these tapering portions are called the "bird's beak").