Effects of gate to drain capacitance to the AC characteristics of trench power MOSFET

For the low voltage power MOSFETs, the power loss and the switching frequency are the most important parameters, the two are separately determined by the conduction resistance R
_DS
(on) and the gate charge Q
_G
. The gate charge mainly depends on the gate to drain charge Q
_GD
. The so-called figure-of-merit, which is defined as the product of the R
_DS
(on) and Q
_GD
is commonly used to quantifying the performance of the power MOSFETs for a specified off-state breakdown voltage (BVDS). The trench gate structure power MOSFET can attain low conduction resistance R
_DS
(on) with high cell density, in this paper its structure and performance are discussed, due to there is a body diode between drain and source, the electrical characteristic of drain and source is not symmetric. On curve tracer, the device's capacitive effects both the gate capacitance and the PN junction capacitance which determines the gate charge Q
_G
are studied with its AC waveform. From this point, some abnormal cases are explained. Its C-V curve is also investigated, for the N- drift area under the gate which forms the gate to drain capacitance C
_GD
, its high frequency C-V curve is different from that of the common MIS structure