The characteristics of a ferroelectric-domain inverted grating fabricated by applying a high-voltage pulse at room temperature in Ti-diffused channel waveguides in z-cut $LiNbO_3$ (Ti:PPLN) were examined for channel waveguide quasi phase-matched secondharmonic generation devices. The fabrication conditions of uniform periodic domain-inversion were examined. Ti:PPLN with period ${Lambda}=16.6{mu}m$ for SHG were fabricated and the performances were measured. A normalized SHG efficiency as high as 473 (%/W) was obtained with 49 mm interaction length.