Method for making a semiconductor device with reduced spacing

摘要

Floating gates are formed in two separate polysilicon depositions steps resulting in distinct portions. The first formed portions are between isolation regions. A thick insulator is formed over the isolation regions and floating gate portions. The thick insulator is patterned to leave fences over the isolation regions. A thinning process, an isotropic etch in this example, is applied to these fences to make them thinner. Polysilicon sidewall spacers are formed on the sides of these fences. These sidewall spacers become the second portion of the floating gate. These second portions have the desired shape for significantly increasing the capacitance to the subsequently formed control gates, thereby reducing the gate voltage required for programming and erasing made by a relatively robust process.