Electrically erasable programmable read-only memory (eeprom) devices including multilayer sense and select transistor gates

Abstract

EEPROM devices include a gate insulating layer and a tunnel insulating layer that is thinner than the gate insulating layer, on an integrated circuit substrate, and a sense transistor gate on the tunnel insulating layer and on the gate insulating layer. The sense transistor gate includes a floating gate on the tunnel insulating layer and on the gate insulating layer, a first interlevel insulating layer on the floating gate opposite the tunnel insulating layer and the gate insulating layer, and a sense gate on the first interlevel insulating layer opposite the floating gate. A select transistor gate also is included on the gate insulating layer and spaced apart from the sense transistor gate. The select transistor gate includes a first select gate on the gate insulating layer that is spaced apart from the sense transistor gate, a second interlevel insulating layer on the first select gate opposite the gate insulating layer, and a second select gate on the second interlevel insulating layer opposite the first select gate that is spaced apart from the sense gate. A first doped region is beneath the tunnel insulating layer and extends to beneath the select transistor gate. A second doped region is beneath the sense transistor gate and is spaced apart from the first doped region. A third doped region is beneath the select transistor gate and is spaced apart from the first doped region. EEPROM devices may be fabricated by forming a gate insulating layer and a tunnel insulating layer that is thinner than the gate insulating layer on an integrated circuit substrate, and a first doped region in the integrated circuit substrate beneath the tunnel insulating layer and beneath a portion of the gate insulating layer. A first conductive layer, an interlevel insulating layer and a second conductive layer are sequentially formed on the tunnel insulating layer and on the gate insulating layer. The second conductive layer, the interlevel insulating layer and the first conductive layer then are patterned, to define a sense transistor gate on the tunnel insulating layer and on the gate insulating layer that comprises a first portion of the first conductive layer, a first portion of the interlevel insulating layer and a first portion of the second conductive layer, and to further define a select transistor gate on the gate insulating layer and spaced apart from the sense transistor gate, that comprises a second portion of the first conductive layer, a second portion of the interlevel insulating layer, and a second portion of the second conductive layer.