This paper reports low-cost microreactor $(10{mu}{ell})$ biochip for the DNA PCR (polymerase chain reaction). The microbiochip $(20mm{ imes}28mm)$ is a hybrid type which is composed of PDMS (polydimethylsiloxane) layer with serpentine micochannel $(360{mu}m{ imes}100{mu}m)$ chamber and glass substrate integrated with microheater and thermal microsensor. Undesirable bubble is usually created during sample loading to PMDS-based microchip because of hydrophobic chip surface. Created bubbles interrupt stable biochemical reaction. We designed improved microreactor chamber using microfluidic simulation. The designed reactor has a coner-rounded serpentine channel architecture, which enables stable injection into hydrophobic surface using micropipette only. Reactor temperature needed to PCR reaction is controlled within ${pm}0.5^{circ}C$ by PID controller of LabVIEW software. It is experimentally confirmed that SRY gene PCR by the fabricated microreactor chip is performed for less than 54 min.