Semiconductor device and forming method, starting circuit and switching power source of semiconductor device

Abstract

The invention provides a semiconductor device and a forming method, a starting circuit and a switching power source of the semiconductor device. The switching power source comprises the starting circuit. The semiconductor device comprises a P-type semiconductor substrate, an N-type drift region, an oxide layer, an intrinsic polycrystalline silicon layer, a doping polycrystalline silicon layer and a metal plug, wherein a source electrode and a drain electrode of a negative threshold field-effect tube are arranged at the two ends of the N-type drift region, the source electrode and the drain electrode are exposed out of the oxide layer, the intrinsic polycrystalline silicon layer is arranged at one end, close to the source electrode, of the oxide layer, and the doping polycrystalline silicon layer is arranged at one end, close to the drain electrode, of the oxide layer. The intrinsic polycrystalline silicon layer and the oxide layer form a grid electrode of the negative threshold field-effect tube, the doping polycrystalline silicon layer forms a resistor connected with the grid electrode, and the metal plug is connected with the drain electrode of the negative threshold field-effect tube and is adjacent to the doping polycrystalline silicon layer. In the semiconductor device, the resistor connected with the drain electrode and the grid electrode of the negative threshold field-effect tube is formed at the position, arranged between the drain electrode and the grid electrode, of the semiconductor substrate and shares the metal plug with the drain electrode, the area of a chip is saved, metal interconnection is reduced through port sharing, and the reliability of the semiconductor device is improved.

Description

technical field

[0001] The invention relates to the field of switching power supplies, in particular to a semiconductor device and its forming method, a starting circuit and a switching power supply including the starting circuit. Background technique

[0002] Currently, switching power supply circuits use PWM (pulse width modulation) control chips to control on or off. The PWM control chip generally integrates high-voltage devices to form a start-up circuit to complete the initial start-up, thereby converting the higher external input voltage into the required lower bias voltage inside the PWM chip.

[0003] US Patent No. 5,581,453 discloses a starting circuit for switching power supplies. The switching power supply also includes a transformer, a switching transistor, a power control circuit and a starting circuit. The switching transistor switches the transformer for periodic connection to the input voltage. The periodic pulses driving the switching transistors are perf...

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