Semiconductor processing method of forming field oxide regions on a semiconductor substrate utilizing a laterally outward projecting foot portion

A semiconductor processing method of forming at least one pair of field oxide regions on a semiconductor substrate comprising the following steps:

• forming a first sacrificial oxide layer over a semiconductor substrate;
• forming a patterned first masking layer over the first sacrificial oxide layer and over a desired active area region of the substrate, the first masking layer comprising a nitride;
• removing exposed portions of the first sacrificial oxide layer;
• after removing the exposed portions of the first sacrificial oxide layer, providing a second sacrificial oxide layer over the exposed substrate;
• forming a layer of silicon over the patterned first masking layer of nitride and over the second sacrificial oxide layer;
• forming a second masking layer over the silicon layer;
• removing a portion of the second masking layer to define at least one pair of second masking layer sidewall spacers over the silicon layer and to outwardly expose portions of the silicon layer, the pair of second masking layer sidewall spacers defining an interconnected pair of masked laterally opposed and laterally outward projecting foot portions of the silicon layer;
• after removing a portion of the second masking layer, removing the exposed portions of the silicon layer to form a pair of silicon sidewall spacers, the pair of silicon sidewall spacers having the pair of laterally opposed and laterally outward projecting foot portions;
• oxidizing the substrate and the silicon sidewall spacers to form at least one pair of field oxide regions on the substrate;
• after the oxidizing step, removing the first masking layer from the substrate;
• after removing the first masking layer from the substrate, removing the second sacrificial oxide layer and any remnants of the first sacrificial oxide layer from the substrate;
• after removing the second sacrificial oxide layer and any remnants of the first sacrificial oxide layer from the substrate, forming a third sacrificial oxide layer over the substrate;
• removing the third sacrificial oxide layer from the substrate;
• and
• after removing the third sacrificial oxide layer from the substrate, forming a gate oxide layer over the substrate.