A memory device includes a semiconductor substrate, memory elements formed above the substrate in rows and columns, bit lines and word lines selectively connected with the memory elements in the respective columns and rows, each memory element including, a first gate insulator formed above the substrate, a charge accumulation layer formed on the first gate insulator, a second gate insulator formed on the charge accumulation layer, and a control electrode formed on the second gate insulator, wherein a ratio r/d is not smaller than 0.5, where r: a radius of curvature of an upper corner portion or surface roughness of the charge accumulation layer and d: an equivalent oxide thickness of the second gate insulator in a cross section along a direction vertical to the bit lines.

Nonvolatile semiconductor memory device and manufacturing method thereof

An integrated memory circuit (chip) and methods for testing the chip. The chip has an array of memory cells, a sense amplifier for reading selected ones of the cells, and a switch having a first state allowing an external device connected to an external pad to sink a reference current from the sense amplifier and a second state disconnecting the pad from the sense amplifier (so that an internally generated reference current can be supplied to the sense amplifier with the switch in the second state). In the first state, the switch preferably is tolerant of a broad and continuous range of voltages on the pad. In some test modes, cells are read using a sense amplifier of the chip while selected voltages are applied to each cell and external equipment sinks reference current flowing from the sense amplifier through an external pad, thus sensing data from each cell with all the timing constraints usually placed on a read of the cell in the normal mode. In one test mode, all wordlines of the array are disabled and a read cycle is performed to measure all columns of the array sequentially while an external reference current flows between external test equipment and a sense amplifier used for performing the read cycle, and the sense amplifier output indicates whether one or more of the columns has leaky cells.

Circuit and method for performing tests on memory array cells using external sense amplifier reference current

A buffer circuit includes a pair of pull-up output transistors (11, 13) and a pair of pull-down output transistors (15, 17) driving an output line (19, 20). Each output transistor is driven by its own tristate input translator (23, 25, 27, 29), all connected to an input terminal (22) of the circuit. Two of the translators (25, 29) are tristated by control signals (51, 52) received as feedback from the output line to turn off one of the pull-up transistors (13) when the output voltage exceeds the high logic level transition voltage (2.2 V) and to turn off one of the pull-down transistors (17) when the output drops below the low logic level transition voltage (0.8 V). This not only prevents ground bounce or overshoot of the output, but also avoids larger current flow or power dissipation from pull-up and pull-down transistors being simultaneously partially on during a transition.

Low noise tri-state output buffer

In order to stably generate a high voltage of a prescribed level, a Vpp detection circuit which is activated in response to an activation signal for comparing the high voltage with a reference voltage is forcibly brought into an active state for a prescribed period under control of an initial control circuit.

Internal high voltage generation circuit capable of stably generating internal high voltage and circuit element therefor

The disclosure is an output buffer capable of preventing a noise by reducing a gradient value of input voltage of an input terminal using a detector which selectively operates only under high supply voltage to reduce a peak value of the current through the pull-up and pull-down transistors of the output buffer, and also capable of achieving an output depending upon the speed by using the conventional circuit under supply voltage less than rated voltage.

High-speed and low-noise output buffer

An internal power voltage generating circuit of a semiconductor memory device may be constructed with a voltage sensing circuit (100) and a reference voltage controller (300) providing an internal power voltage int. VCC of a given reference voltage amplitude Vref and an external power voltage amplitude ext. VCC. Thus, when a high voltage over an operating voltage of a chip is applied to a pad (10) of the chip, the internal power voltage is raised to the level of the external power voltage. Therefore, when stress is added to the chip during a "burn-in-test", the defective chip is easily detected. Consequently, the reliability of those semiconductor memory devices subjected to post-manufacturing testing can be improved.

Electrically programmable internal power voltage generating circuit

A data output buffer suitable for use in a semiconductor memory device includes a first input circuit coupled to a first data signal and a first control signal, e.g., an output enable signal, and a second input circuit coupled to a second data signal which is the inverse of the first data signal and the first control signal. The data output buffer also includes a pull-up circuit responsive to the output of the first input circuit for selectively raising the data output node to a high voltage level, e.g., Vcc, and a pull-down circuit responsive to the output of the second input circuit for selectively lowering the data output node to a low voltage level, e.g., Vss. The data output buffer further includes a preset circuit comprised of a first preset control circuit responsive to the output of the first input circuit and a second control signal, e.g., an inverse output enable signal, for selectively raising the data output node from the low voltage level to an intermediate voltage level, e.g., 1/2 Vcc, and a second preset control circuit responsive to the output of the second input circuit and the second control signal for selectively lowering the data output node from the high voltage level to the intermediate voltage level. The preset control circuit advantageously operates to maintain the data output node at the intermediate voltage level during active states of the output enable signal without generating any DC current, thereby eliminating the noise and reliability problems of presently available data output buffers.

Tristate data output buffer having reduced switching noise and intermediate-level setting

For a SRAM having a sense amplifier amplifying memory data and a read/write control circuit controlling operations of the sense amplifier, a data output buffer circuit is provided, which includes: a drive output node from which data output buffer provides output data; a first circuit providing a NOR function of an SAS signal from the sense amplifier and an output enable signal (OE) from the read/write control circuit; a second circuit providing a NOR function of an SAS signal from the sense amplifier and the output enable signal (OE) from the read/write control circuit; a third circuit eliminating noise produced by transition in the outputs of the first and second circuit and also enhancing a response time; a fourth circuit inverting the output of the first circuit; a fifth circuit inverting twice, sequentially, the output of the second circuit; and a sixth circuit responsive to the fourth and fifth circuit, alternatively providing, depending on the SAS and an SAS signal from the sense amplifier, one of three states on the drive output node: a first and second output state, and a third high impedance state. None of the first, second, third, fourth, fifth, and sixth circuit requires use of a single pulse output signal externally provided to the data output buffer circuit. During transition from the first state to the second state, the drive output node passes through the third high impedance state.

Yong-Bo Park

Papers

Electrically programmable internal power voltage generating circuit

Tristate data output buffer having reduced switching noise and intermediate-level setting

Data output buffer circuit for a SRAM

Elektrisch programmierbarer zur internen stromversorgungserzeugung geeigneter schaltkreis

Power voltage generating circuit