| 摘要 |
An embodiment of the instant invention is a transistor formed on a semiconductor substrate of a first conductivity type and having an upper surface, the transistor comprising: a well region (well 204 of FIG. 1a) formed in the semiconductor substrate (layer 202 of FIG. 1a), the well region of a second conductivity type opposite that of the first conductivity type; a source region (source region 208 of FIG. 1a) formed in the well region in the semiconductor substrate, the source region of the second conductivity type; a drain region (drain 210 of FIG. 1a) formed in the semiconductor substrate and spaced away from the source region by a channel region (given by length L1+L2), the drain region of the second conductivity type; a conductive gate electrode (layer 218 of FIG. 1a) disposed over the semiconductor substrate and over the channel region; a gate insulating layer (layer 214 of FIG. 1a) disposed between the conductive gate electrode and the semiconductor substrate and having a length, the gate insulating layer comprising: a first portion of the gate insulating layer which has a first length (L1) and a first thickness; a second portion of the gate insulating layer which has a second length (L2) and a second thickness which is substantially thicker than the first thickness, the sum of the first length and the second length equalling the length of the gate insulating layer; and wherein the first portion of the gate insulating layer being situated proximate to the source region and spaced away from the drain region by the second portion of the gate insulating layer; and wherein the well region having a dopant concentration less than that of the source region and the drain region, the well region extends at least from source region towards the drain region so as to completely underlie the first portion of the gate insulating layer and to underlie at least the second portion of the gate insulating layer.
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