Semiconductor memory device and method for producing same

Abstract

A semiconductor memory device with improved operational reliability, and a method for fabricating the device. The semiconductor memory device includes a select gate 3 a, arranged in a first area on a substrate 1 , floating gates 6 a arranged in a second are,a adjacent to the first area, first and second diffusion areas 7 a, 7 b arranged in a third area adjacent to the second area, and a control gate 11 arranged on the top of the floating gates 6 a. The upper end faces of the floating gates 6 a are planarized.

Description

technical field [0001] The present invention relates to a semiconductor memory device having cell transistors and a manufacturing method thereof, and more particularly to a semiconductor memory device storing a plurality of bits of information per cell and a manufacturing method thereof. Background technique [0002] Among conventional semiconductor memory devices, a nonvolatile semiconductor memory device having a cell transistor as shown in FIG. 8 (conventional example 1) is known. In the nonvolatile semiconductor memory device of Conventional Example 1, in an AND-type flash memory having a plurality of nonvolatile memory cells, the respective cross-sectional shapes of the plurality of floating gate electrodes 106G are formed to be smaller than those of the first embodiment. The electrode 104G has a high convex shape, wherein the plurality of nonvolatile memory cells have a plurality of first electrodes 104G, a plurality of word lines 105 intersecting therewith, and a plur...

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Problems solved by technology

In addition, since the floating gate 206a is easily affected by variations in etch-back (see FIG. 12(E)), there is a risk of variations in the shape and height of the floating gate 206a (the position of the corner 206b).

In particular, the vicinity of the upper end of the sidewall-shaped curved surface of the floating gate 206a is more likely to be affected by variations in etch back than the vicinity of the lower end, and is more likely to be damaged by etch back.

Therefore, there is a risk of reduced operational reliability.

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