Method of forming transistor using step STI profile in memory device
First Claim
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1. A method of forming a memory device, comprising:
- forming first and second isolation structures on a semiconductor substrate, the first and second isolation structures defining an active region therebetween;
forming STI spacers on sidewalls of the first and the second isolation structures;
forming a trench having a width narrower than a distance between the first isolation structure and the second isolation structure to form a step profile in the active region by etching the semiconductor substrate using the STI spacers as an etching mask; and
forming a doped region to be used as a source region or a drain region in a bottom side of the trench and in a sidewall of the trench by performing an ion implantation process,wherein the doped region is formed after forming the first and second isolation structures.
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Abstract
A method of forming a memory device includes forming first and second isolation structures on a semiconductor substrate, the first and second isolation structures defining an active region therebetween; and etching a portion of the semiconductor substrate provided within the active region to define a step profile, so that the active region includes a first vertical portion and an upper primary surface, the first vertical portion extending above the upper primary surface.
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11 Claims
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1. A method of forming a memory device, comprising:
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forming first and second isolation structures on a semiconductor substrate, the first and second isolation structures defining an active region therebetween; forming STI spacers on sidewalls of the first and the second isolation structures; forming a trench having a width narrower than a distance between the first isolation structure and the second isolation structure to form a step profile in the active region by etching the semiconductor substrate using the STI spacers as an etching mask; and forming a doped region to be used as a source region or a drain region in a bottom side of the trench and in a sidewall of the trench by performing an ion implantation process, wherein the doped region is formed after forming the first and second isolation structures. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
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9. A method of forming a memory device, comprising:
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forming first and second isolation structures on a semiconductor substrate, the first and second isolation structures defining an active region therebetween; forming first and second spacers provided adjacent to the first and second isolation structures, respectively, the first and second spacers exposing a portion of the substrate; etching the exposed portion of the substrate to define a step profile, so that the active region includes first and second vertical portions and an upper primary surface, the first and second vertical portions extending above the upper primary surface, the first vertical portion being provided directly below the first spacer, the second vertical portion being provided directly below the second spacer; forming a doped region to be used as a source region or a drain region in a bottom side of the step profile and in a sidewall of the step profile by performing an ion implantation process, wherein the doped region is formed after forming the first and second isolation structures; annealing the semiconductor substrate after the etching step to round a corner defined by the step profile; removing an oxide film formed over the substrate as a result of the annealing; and thereafter, forming a tunnel oxide over the semiconductor substrate within the active region, wherein the tunnel oxide is formed using a radical oxidization process. - View Dependent Claims (11)
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Specification