Abstract of the Disclosure

A method for producing deeply recessed oxidized regions in silicon. A series of deep trenches are formed in a silicon wafer by a reactive ion etching (RIE) method. In a first species, the trenches are of equal width. A block-off mask is selectively employed during part of the RIE process to produce trenches of unequal depth. The trench walls are thermally oxidized to completely fill in all of the trenches with oxide at the same time. In a second species, the trenches are of equal depth and width and of uniform spacing. In one aspect of the second species, the width of the trenches is equal to the distance between the trenches whereby the thermal oxidation completely fills in the trenches with oxide at the same time that the silicon between the trenches is fully converted to silicon oxide. In another aspect of the second species, the trenches are wider than the distance between the trenches whereby the thermal oxidation only partially fills in the trenches with oxide when the intervening silicon is fully converted to silicon oxide. In the latter aspect, the filling of the trenches is completed by the deposition of suitable material such as pyrolytically deposited silicon oxide

• a series of simplified cross-sectional views of the formation of dielectrically filled trenches of different depths at various stages of the method of the present invention.

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