Hi,
I have designed H-bridge and added circuit of H-bridge. Switching frequencu is 20 kHz. Mosfet gate signal has spikes. You think, what is the problem ?
Probably not, at least not with the shown waveform. Your oscilloscope waveform has spikes. But are they real?
There are many previous threads about gate driver and measurement problems. As a first step, you should describe the circuit layout, e.g. by photos and explain how the signals are probed.
before dc voltage is applied to the input of the circuit, mosget gate signal has not spikes but spikes occur when dc voltage is applied to input of circuit. Oscilloscope waveform is obtained with differential probe.