Methods of forming semiconductor devices including multistage planarization and crystalization of a semiconductor layer

A method of forming a semiconductor device, comprising:

• forming a pattern on a semiconductor substrate, the pattern having a top surface and trenches exposing the semiconductor substrate;
• forming an amorphous semiconductor layer that fills the trenches and covers all of the top surface of the pattern;
• planarizing the amorphous semiconductor layer without exposing the pattern to form a planarized amorphous semiconductor layer that covers all of the top surface of the pattern;
• crystallizing the planarized amorphous semiconductor layer to form a crystalline semiconductor layer having a raised portion disposed on the top surface of the pattern;
• and
• planarizing the crystalline semiconductor layer until the pattern is exposed to form a crystalline semiconductor pattern.