A nonvolatile semiconductor memory device comprises: a substrate; a memory cell that is disposed on the substrate and accumulates a charge as data; and a cover layer covering the memory cell. The cover layer has a structure in which a first silicon nitride layer, an intermediate layer, and a second silicon nitride layer are stacked sequentially from a memory cell side.

A method of forming an integrated DMOS transistor/EEPROM cell includes forming a first mask over a substrate, forming a drift implant in the substrate using the first mask to align the drift implant, simultaneously forming a first floating gate over the drift implant, and a second floating gate spaced apart from the drift implant, forming a second mask covering the second floating gate and covering a portion of the first floating gate, forming a base implant in the substrate using an edge of the first floating gate to self-align the base implant region, and simultaneously forming a first control gate over the first floating gate and a second control gate over the second floating gate. The first floating gate, first control gate, drift implant, and base implant form components of the DMOS transistor, and the second floating gate and second control gate form components of the EEPROM cell.

A nonvolatile memory device may include: an isolation layer formed in a substrate and defining an active region; a control plug formed over the isolation layer; a floating gate formed over the substrate and including a plurality of fingers adjacent to the control plug with a gap provided therebetween; and a charge blocking layer formed on sidewalls of the floating gate so as to fill the gap. The control plug may include: a first control plug formed between the plurality of fingers and having sidewalls facing inner walls of the fingers; and a second control plug formed outside the floating gate and having sidewalls facing outer walls of the fingers.

A semiconductor device includes a substrate, a first transistor, and a second transistor. The first transistor includes a first source terminal formed of a material and connected to a first source, a first drain terminal formed of the material and connected to a first drain, a first gate overlapping a portion of the substrate that is between the first source and the first drain, and a first dielectric layer between the first gate and the substrate. The second transistor includes a control gate formed of the material and overlapping a part of the substrate that is positioned between a second source and a second drain, a second dielectric layer between the control gate and the substrate, a floating gate extending through the second dielectric layer to contact a doped region in the substrate, and an insulating member positioned between the control gate and the floating gate.